@@ -1,16 +1,16 @@
 ## 7.1 Check Prime:
 
-### S-1: The problem
+### The problem
 For a given number, check whether the number is a prime number or not.
 
-### S-2: Hint
+###  Hint
 A number is a prime number. If that number is only divisible by 1 and the number itself.
 
 This means a prime number is not divisible by any numbers between 1 and the number itself.
 
 So, to check prime, you can start dividing the number from 2. And then increase it by 1. If the number gets divided, then it’s not a prime number.
 
-### S-3: The solution
+###  The solution
 
 ```python
 def is_prime(num):
@@ -32,7 +32,7 @@ else:
 
 [Try it on Programming Hero button]
 
-### S-4: Explanation
+###  Explanation
 The core part of the algorithm is the is_prime function.
 
 There we start a for loop the range(2, num). Because we want to know that the number is not divisible by any number except 1 or the number itself.
@@ -49,10 +49,10 @@ If the number doesn’t get divided by any numbers smaller than the number, it w
 
 Then we will return True. Because it didn’t get divided, by any numbers. Hence, it will be a prime number.
 
-### S-5: Many Solution
+###  Many Solution
 There are other solutions to this problem as well. We encourage you to google, “check prime number python”. In that way, you will learn a lot.
 
-### S-6: Take Away
+###  Take Away
 A prime number is only divisible by 1 and the number itself.
 
  

@@ -1,14 +1,14 @@
 ## 6.3 Calculate grades
 
-### S-1: The problem
+### The problem
 Calculate grade of five subjects.
 
-### S-2: Hint
+###  Hint
 So, you have to take five inputs. These will be the marks of five subjects. Then, create the average.
 
 Once you have the average. It just running an if-else. And decide the grade.
 
-### S-3: The Solution
+###  The Solution
 ```python
 print('Enter your marks:')
 sub1=int(input("First subject: "))
@@ -32,7 +32,7 @@ else:
 ```
 **[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
 
-### S-4: Explanation
+###  Explanation
 Calculation of average is easy. Add them all and then divide by the count. As we are taking numbers for 5 subjects we are dividing the total by 5.
 
 After that, we are running a simple if-else to determine the grade.

@@ -1,16 +1,16 @@
 ## 6.2: Compound Interest
 
-### S-1: The Problem
+### The Problem
 Take money borrowed, interest and duration as input. Then, compute the compound interest rate.
 
-### S-2: Hint
+###  Hint
 Compound interest formula is:
 
 A = P(1+r/100)t
 
 Here, P is the principal amount; it is the amount that you borrowed. r is the interest rate in percentage and t is the time.
 
-### S-3: Solution
+###  Solution
 
 ```python
 def compound_interest(principle, rate, time):
@@ -28,14 +28,14 @@ print("Interest Amount is:", total_due)
 
 **[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
 
-### S-4: Explanation
+###  Explanation
 Inside the function, just look into the power calculation.
 
 **(1 + rate / 100) time**
 
 Rest of the part should be easy for you.
 
-### S-5: Take Away
+###  Take Away
 To apply the same power on multiple things, put them inside parentheses and then apply the power.
 
 

@@ -1,9 +1,9 @@
 ## 6.4 Gravitational Force
 
-### S-1: The Problem
+### The Problem
 Compute gravitational force between two objects.
 
-### S-2: Hint
+###  Hint
 The formula for gravitational force is
 
 **F = G m1m2/r2**
@@ -12,7 +12,7 @@ Here G is the gravitational constant. Its value is 6.673*10-11
 
 So, take three input from the users. The mass of the first object, the mass of the second object and the distance between them.
 
-### S-3: Solution
+###  Solution
 
 ```python
 mass1 = float(input("First mass: "))
@@ -28,7 +28,7 @@ print("The gravitational force is:", round(force, 5),"N")
 
 **[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
 
-### S-4: Explanation
+###  Explanation
 The calculation is simple. Only two things need to be learned from this.
 
 **Have a look, how we wrote 6.673*10-11**

@@ -2,16 +2,16 @@
 
 ---
 
-### S-1: The Problem
+### The Problem
 You borrowed $5000 for 2 years with 2% interest per year.
 Calculate the simple interest to know how much you have to pay?
 
-### S-2: Hint
+###  Hint
 Just take amount, duration and interest rate.
 
 You have to multiply these three. And, don’t forget: you have to convert percent to a fraction by dividing it by 100.
 
-### S-3: The Solution
+###  The Solution
 
 ```python
 principle = int(input("Money you borrowed: "))
@@ -26,7 +26,7 @@ print("Simple interest is:", simple_interest)
 
 **[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
 
-### S-4: Explanation
+###  Explanation
 Read the code. I think you don’t need any extra explanation here.
 
 

@@ -1,10 +1,10 @@
-## 6.5 Triangle Area
+## Triangle Area
 ---
 
-### S-1: The Problem
+### The Problem
 Take three sides of a triangle. And then calculate the area of the triangle.
 
-### S-2: How it works
+### How it works
 To calculate the area of the triangle. First, calculate the half of the perimeter. Here perimeter is the sum of each side of the triangle.
 
 Let’s call it s.
@@ -16,7 +16,7 @@ s = (a+b+c)/2
 area = √(s(s-a)*(s-b)*(s-c))
 ```
 
-### S-3: the code
+### the code
 ```python
 import math
 
@@ -33,7 +33,7 @@ print('Area of your triangle is ', area)
 ```
 **[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
 
-### S-4: Explanation
+### Explanation
 To calculate the square root. We used the math module. And call math.sqrt.
 
 ```python
@@ -47,16 +47,19 @@ Similarly, math.sqrt(25) will give 5 as output.
 
 This is something new you have learned this time.
 
-### S-5: Quiz
+### Quiz
 
-1. How would you calculate the square root of a number.
-2. Use math.square.root
-3. Use math.sqroot
-4. Use math.sqrt
+How would you calculate the square root of a number.
+1. Use math.square.root
+2. Use math.sqroot
+3. Use math.sqrt
 
-**The answer is: 3**
+<details>
+<summary><b>Show Answer</b></summary>
+<p>The answer is: 3</p>
+</details>
 
-### S-6: Take Away
+### Take Away
 The math module has a lot of math-related functionalities.
 
 

@@ -1,6 +1,6 @@
 ## 4.2 Celsius to Fahrenheit
 
-### S-1: The problem
+### The problem
 Take the temperature in degrees Celsius and convert it to Fahrenheit.
 
 <details>
@@ -12,7 +12,7 @@ Take the temperature in degrees Celsius and convert it to Fahrenheit.
 
 Think for a second...How will you multiply a variable by 9 and then divide by 5? and then add 32. Can you do it without looking at the solution?
 
-### S-3: The solution
+###  The solution
 ```python
 celsius = float(input("Enter temperature in degrees Celsius: "))
 

@@ -1,6 +1,6 @@
 ## 4.4: Decimal to Binary (recursive)
 
-### S-1: The Problem
+### The Problem
 Convert a decimal number to binary number using a recursive function.
 <details>
 <summary><b>S-3: Click Here For Show Hints</b></summary>
@@ -9,7 +9,7 @@ Convert a decimal number to binary number using a recursive function.
 So, don’t worry if you felt confused. You are not alone. I am in the same condition as well.</p>
 </details>
 
-### S-3: Recursive
+###  Recursive
 
 ```python=
 def dec_to_binary(n):
@@ -27,7 +27,7 @@ print(" ")
 
 **[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
 
-### S-4: Explanation
+###  Explanation
 The core part of the logic is simple. If the number is greater than 1, call the dec_to_binary function again. And, while calling, send the result of dividing operation as the input number.
 
 If you remember, the while loop in the previous code problem is similar. In the while loop, we were going back to the next iteration with n = n//2
@@ -40,7 +40,7 @@ While printing, we have one extra thing called end=''.
 The purpose of end='' is to print the output in the same line. If you don’t add end='', every print output will be displayed in a new line.
 
 
-### S-6: Take Away
+###  Take Away
 There are multiple ways to format the print string. Google it, when needed.
 
 

@@ -1,9 +1,9 @@
 ## 4.4: Decimal to Binary
 
-### S-1: The Problem
+### The Problem
 Convert a decimal number to binary number.
 
-### S-2: Decimal vs Binary
+###  Decimal vs Binary
 
 The numbers that we use every day is called decimal number. A decimal number could have any of the 10 digits (0, 1, 2, 3, 4,5 6, 7, 8, 9).
 
@@ -34,7 +34,7 @@ Then you will reverse the list.
 Finally, you have to put the binary bits (0 and 1) in one number to get the final binary. </p>
 </details>
 
-### S-4: Solution
+###  Solution
 I looked into the below code 7 times to understand. Still trying to figure it out...So, spend some time here to look at the code:
 
 ```python
@@ -58,7 +58,7 @@ print("Your binary is:", binary)
 ```
 **[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
 
-### S-5: Explanation
+###  Explanation
 You have seen the remainder and dividing the number with // before. That is the core part of this decimal to a binary algorithm.
 
 So, this part should be easier for you:
@@ -89,16 +89,19 @@ Try to read this explanation and code multiple times. And, if needed, come back
 If you keep trying and revisiting , again and again, these will start making sense.
 
 
-### S-6: Quiz
+###  Quiz
 
 1. What is a binary number?
 2. Numbers written on a trash bin
 3. Numbers that use 0,1 only
 4. Numbers with any 2 digits
 
-#### The answer is : 2
+<details>
+<summary><b>Show Answer</b></summary>
+<p>The answer is : 2</p>
+</details>
 
-### S-7: Take Away
+###  Take Away
 Binary numbers use 0 and 1 only.
 
 

@@ -1,6 +1,6 @@
 ## 4.1: Miles to Kilometers
 
-#### S-1: The Problem
+#### The Problem
 Convert miles to kilometers.
 
 <details>
@@ -12,7 +12,7 @@ Convert miles to kilometers.
 Now, think what you can do with this information. </p>
 </details>
 
-### S-3: The solution
+###  The solution
 
 ```python
 miles = float(input("Enter distance in miles: "))
@@ -22,7 +22,7 @@ print("Distance in Kilometers:", kilometers)
 
 **[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
 
-### S-4: Explanation
+###  Explanation
 Just take a number from the user. Allow the user to enter a float number. Then, multiply that number by 1.609344. Keep the multiplication in the kilometers variable.
 
 The kilometers is your answer.