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

Input: Consider Input: 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

Output: 11 / 6


Input: Consider Input: Problem: find the least number must be subtracted from 105829 so that remaining no . is divisible by 21 ?

Output: 10


Input: Consider Input: Problem: a hiker walked for 3 days . she walked 18 miles on the first day , walking 3 miles per hour . on the second day she walked for one less hour but she walked one mile per hour , faster than on the first day . on the third day 5 miles per hour for 6 hours . how many miles in total did she walk ?


Output: 68