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

[EX Q]: Problem: what is the probability of getting a queen or spade from a set of cards ?
[EX A]: 4 / 13

[EX Q]: Problem: a grocer is storing soap boxes in cartons that measure 25 inches by 42 inches by 60 inches . if the measurement of each soap box is 7 inches by 6 inches by 10 inches , then what is the maximum number of soap boxes that can be placed in each carton ?
[EX A]: 150

[EX Q]: Problem: 63 persons can repair a road in 12 days , working 5 hours a day . in how many days will 30 persons , working 6 hours a day , complete the work ?
[EX A]:
21