The task is to generate the correct answer for a given math problem.

Ex Input:
Problem: a sum of money at simple interest amounts to rs . 815 in 3 years and to rs . 878 in 4 years . the sum is :

Ex Output:
626


Ex Input:
Problem: if the cost price of 50 articles is equal to the selling price of 40 articles , then the gain or loss percent is ?

Ex Output:
25 %


Ex Input:
Problem: car dealership x , the total profit from sales increased by 8 percent over the previous years , while the number of cars sold decreased by 8 percent over the previous years . approximately what was the average percent increase in profit per car over the previous year .

Ex Output:

17.39 %