Charlie, Warren, Oliver and Jack paid a total of $90 for a souvenir. Jack paid ²₃ of what the rest paid. Charlie paid 50% of what the rest paid. Warren and Oliver paid an equal amount of money. How much did Oliver pay?

Charlie	Warren	Oliver	Jack	Total
3x3			2x3	5x3
1x5	2x5			3x5
	1	1
5 u	2 u	2 u	6 u	15 u

50%= ⁵⁰₁₀₀= ¹₂
Charlie's share : Total share = 1 : 2

The total amount paid for the souvenir is repeated.  Make the total amount the same.  LCM of 5 and 3 is 15.

Amount that Warren, Oliver and Jack paid = 10 u

Amount that Warren and Oliver paid
= 10 u - 6 u
= 4 u

The amount that Warren and Oliver each paid is the same.

Amount that Warren and Oliver each paid
= 4 u ÷ 2
= 2 u

Cost of the souvenir = 15 u

15 u = 90

1 u = 90 ÷ 15 = 6

Amount that Oliver paid
= 2 u
= 2 x 6
= $12

Answer(s): $12