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

Ex Input:
Problem: the sum of ages of 5 children born 1 years different each is 30 years . what is the age of the elder child ?

Ex Output:
8


Ex Input:
Problem: 30 pens and 75 pencils were purchased for 750 . if the average price of a pencil was 2.00 , find the average price of a pen .

Ex Output:
20


Ex Input:
Problem: solve below question 2 x + 1 = - 13

Ex Output:

-