Oliver and Juan had $66 altogether. Juan had $24 less than Oliver. After Juan spent some money at the store, Oliver had 3 times as much money as Juan. How much money had Juan spent at the store?
O + J = 66
O - J = 24 add these
2O = 90
O = 90 / 2 = $45 = what Oliver had at all times
J = $21 = what Juan had at first
Juan had (1/3)O = (1/3) (45) = $ 15 after the store
He spent 21 - 15 = $ 6 at the store
