John's annual salary after a raise of 15% is $45,000. What was his salary before the raise?

When an original amount or any other quantity is increased or raised by a given percentage the relationship between the original and the increased amount is given by the following formula.

x' = x*(100+p)/100   ...   (1)

Or

x = x'*100/(100+p)   ...   (2)

Where:

x = original amount

x' = increased amount

p = percentage increase

In the question it is given that:

Salary after raise = x' = $45000

Percentage raise = p = 15

We have to find salary before raise, that is x.

Substituting values of x' and p in the formula (2) we get:

x = 45000*100/(100 + 15) = 4500000/115 = 39130.43

Answer:

John's salary before raise was $39130.43