The difference between the two numbers is 20% of the larger number. If the smaller number is 12, the larger one is:

Question: The difference between the two numbers is 20% of the larger number. If the smaller number is 12, the larger one is:

Solution:
Let the number be x

Then,
x − 12 = 20% of x
⇒ x − 12 = x/5
⇒ x − x/5 = 12
⇒ 4x/5 = 12
⇒ x = (12 × 5)/4
∴ x = 15