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

Ex Input:
Problem: a swimmer can swim in still water at 4 km / h . if the speed of the water current is 2 km / h , how many hours will the swimmer take to swim against the current for 5 km ?

Ex Output:
2.5


Ex Input:
Problem: 90 % of the population of a village is 36000 . the total population of the village is ?

Ex Output:
4000


Ex Input:
Problem: working alone , printers x , y , and z can do a certain printing job , consisting of a large number of pages , in 12 , 25 , and 30 hours , respectively . what is the ratio of the time it takes printer x to do the job , working alone at its rate , to the time it takes printers y and z to do the job , working together at their individual rates ?

Ex Output:

150 / 11