Zoe, Pamela, Hazel and Julie jointly contributed to the cost of a present for their sister. Zoe's contribution is ²₃ of the total contribution made by the four girls. The ratio of Julie's contribution to the total of Pamela's and Hazel's contribution is 3 : 1. What is the total contribution by the four girls if Pamela's contribution is ²₃ of Hazel's contribution and the total amount contributed by Zoe and Julie is $660?

Zoe	Pamela	Hazel	Julie	Total
2x20	1x20			3x20
	1x5		3x5
	2x1	3x1
40 u	2 u	3 u	15 u	60 u

Working backwards.

Total amount that Pamela and Hazel had is the combined repeated identity.
LCM of 1 and 5 = 5

Total amount that Pamela, Hazel and Julie had is the next combined repeated identity.
LCM of 1 and 20 = 20 

Total amount contributed by Zoe and Julie
= 40 u + 15 u
= 55 u

55 u = 660

1 u = 660 ÷ 55 = $12

Total contribution by the four girls
= 60 u
= 60 x 12
= $720

Answer(s): $720