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

[EX Q]: Problem: how many quarters are equal to 7 dollars ?
[EX A]: 28

[EX Q]: Problem: john left home and drove at the rate of 45 mph for 2 hours . he stopped for lunch then drove for another 3 hours at the rate of 45 mph to reach his destination . how many miles did john drive ?
[EX A]: 225 miles .

[EX Q]: Problem: a can do a piece of work in 80 days . he works at it for 10 days b alone finishes the remaining work in 42 days . in how much time will a and b working together , finish the work ?
[EX A]:
30