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

[Q]: Problem: a bag contains 12 red marbles . if someone were to remove 2 marbles from the bag , one at a time , and replace the first marble after it was removed , the probability that neither marble would be red is 25 / 36 . how many marbles are in the bag ?
[A]: 48


[Q]: Problem: the average age of 10 men is increased by years when two of them whose ages are 21 years and 23 years are replaced by two new men . the average age of the two new men is
[A]: 3


[Q]: Problem: calculate how long it will take a swimmer to swim a distance of 12 km against the current of a river which flows at 1.2 km / hr , given that he can swim in still water at 5 km / h
[A]:
3.16