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

Example Input: Problem: the sum of ages of 5 children born at the intervals of 3 years each is 55 years . what is the age of the youngest child ?
Example Output: 5 years

Example Input: Problem: set s contains exactly 10 numbers and has an average ( arithmetic mean ) of 6.2 . if one of the numbers in set s is increased by 7 , while all other numbers remain the same , what is the new average of set s ?
Example Output: 6.

Example Input: Problem: in a group of cows and chickens , the number of legs was 12 more than twice the number of heads . the number of cows was :
Example Output:
6