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

Example Input: Problem: when positive integer n is divided by positive integer p , the quotient is 18 , with a remainder of 7 . when n is divided by ( p + 3 ) , the quotient is 15 and the remainder is 1 . what is the value of n ?
Example Output: 20

Example Input: Problem: two trains of length 100 meters and 200 meters are 450 meters apart . they are moving towards each other on parallel tracks , at speeds of 90 km / h and 72 km / h . after how many seconds will the trains meet ?
Example Output: 10

Example Input: Problem: if the cost price of 60 articles is equal to the selling price of 40 articles , then what is the percent profit ?
Example Output:
50 %