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

Problem: if a - b = 6 and a 2 + b 2 = 50 , find the value of ab .
a ) 7

Problem: the ratio of a to b is 4 to 5 , where a and b are positive . if x equals a increased by 25 percent of a , and m equals b decreased by 60 percent of b , what is the value of m / x ?
2 / 5

Problem: the number of diagonals of a polygon of n sides is given by the formula v = n ( n - 3 ) / 2 . if a polygon has twice as many diagonals as sides , how many sides does it have ?

5