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

Ex Input:
Problem: what is the probability of getting a queen or spade from a set of cards ?

Ex Output:
4 / 13

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

Ex Output:
30 %

Ex Input:
Problem: 4 balls of different colors are to be placed in 3 different boxes such that any box contains at least 1 ball . what is the maximum number of different ways in which this can be done ?

Ex Output:
18