At the start, Ben and Rick have the same amount of money. Let x represent that amount.
Rick's money: x
Ben's money: x
Then, Ben spends $138.
Rick's money: x
Ben's money: x - 138
At that point, Rick has 4 times the amount that Ben has.
x = 4(x - 138)
x = 4x - 552
552 = 3x
184 = x
Rick has $184.
