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

Example Input: Problem: if 1.5 cm of a pencil is purple , 0.5 cm of the remaining is black and the remaining 2 cm is blue , what is the total length of the pencil ?
Example Output: 4 cm

Example Input: Problem: students at a school were on average 180 cm tall . the average female height was 170 cm , and the average male height was 182 cms . what was the ratio of men to women ?
Example Output: 5 : 1

Example Input: Problem: if a - b = 6 and a 2 + b 2 = 50 , find the value of ab .
Example Output:
a ) 7