instruction:
The task is to generate the correct answer for a given math problem.
question:
Problem: how many prime numbers are between 51 / 13 and 89 / 9 ?
answer:
2

question:
Problem: one half of a two digit number exceeds its one third by 7 . what is the sum of the digits of the number ?
answer:
e ) 1

question:
Problem: today mary ' s father is 4 times as old as mary . 3 years ago , he was 5 times as old . how old is mary today ?
answer:
12