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

Q: Problem: a number x is 5 times another number y . the percentage that y is less than x is

A: 80 %
****
Q: Problem: if 4 xz + yw = 10 and xw + yz = 20 , what is the value of the expression ( 2 x + y ) ( 2 z + w ) ?

A: 50 .
****
Q: Problem: the area of a square field is 625 km 2 . how long will it take for a horse to run around at the speed of 25 km / h ?

A:
4 h
****