Initially, Ben had 7x coins; William had 5x coins.
After giving 12 coins from Ben to William
7x - 12 = 5x + 12
Simplify and find x
7x - 5x = 12 + 12
2x = 24
x = 24/2 = 12.
ANSWER. Initially, Ben had 7*12 = 84 coins; William had 5*12 = 60 coins.