Clay and Timmy had $318 altogether. Timmy had $18 less than Clay. After Timmy spent some money at the store, Clay had 6 times as much money as Timmy. How much money had Timmy spent at the store?
+237 Let x = Clay's money
Let y = Timmy's money
x + y = 318 (1)
y = x - 18 (2)
Substitute (2) to (1):
x + x - 18 = 318
2x/2 = 336/2
x = 168
From (2): y = x - 18
y = 168 - 18
y = 156
Let z = amount of money Timmy spent at the store
(150 - z) = 168
900 - 6z = 168
732/6 = 6z/6
z = $122
