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

Example Input: Problem: a and b can together finish a work in 40 days . they worked together for 10 days and then b left . after another 15 days , a finished the remaining work . in how many days a alone can finish the job ?
Example Output: 2

Example Input: Problem: a dealer purchases 15 articles for rs . 25 and sells 12 articles for rs . 32 . find the profit percentage ?
Example Output: 60 

Example Input: Problem: in a group of 90 students , 30 are taking history , and 32 are taking statistics . if 59 students are taking history or statistics or both , then how many students are taking history but not statistics ?
Example Output:
33