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

Ex Input:
Problem: by selling an article for $ 195 , a person gains $ 45 . what is the gain % ?

Ex Output:
30 %


Ex Input:
Problem: pipe a can fill a tank in 6 hours . due to a leak at the bottom , it takes 10 hours for the pipe a to fill the tank . in what time can the leak alone empty the full tank ?

Ex Output:
15


Ex Input:
Problem: the population of a town increased from 1 , 75,000 to 2 , 97,500 in a decade . the average percent increase of population per year is

Ex Output:

7