Question 980812
Bill is x
Ben is 91-x

number of years between the two is x-(91-x)=2x-91
When Bill was Ben's age, 2x-91 years ago, Bill was x-(2x-91)=91-x years old.
That 91-x is 2*the age of Ben at that time.
Ben is 91-x, and from that is subtracted 2x-91.  That makes Ben 182-3x years old.

Therefore, 91-x=2(182-3x)
91-x=364-6x
5x=273
x=54.6
91-x=36.4
18.2 years ago, Bill was 36.4 years old, Ben's age, and Ben was 18.2 years old, half as much.

Bill is 54.6 years old
Ben is 36.4 years old