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

[EX Q]: Problem: the ratio of a to b is 4 to 5 , where a and b are positive . if x equals a increased by 25 percent of a , and m equals b decreased by 60 percent of b , what is the value of m / x ?
[EX A]: 2 / 5

[EX Q]: Problem: the average of first 10 odd numbers is ?
[EX A]: 10

[EX Q]: Problem: a group of hikers is planning a trip that will take them up a mountain using one route and back down using another route . they plan to travel down the mountain at a rate of one and a half times the rate they will use on the way up , but the time each route will take is the same . if they will go up the mountain at a rate of 7 miles per day and it will take them two days , how many miles long is the route down the mountain ?
[EX A]:
21