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

Q: Problem: a can do a work in 15 days and b in 20 days . if they work on it together for 7 days , then the fraction of the work that is left is

A: 11 / 6
****
Q: Problem: if each side of a square is increased by 20 % , find the percentage change in its area ?

A: 44 %
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Q: Problem: what is the greatest positive integer e such that 3 ^ e is a factor of 9 ^ 10 ?

A:
e = 20
****