Gillian, Joelle, Mary and Kylie jointly contributed to the cost of a present for their classmate. Gillian's contribution is ³₇ of the total contribution made by the four girls. The ratio of Kylie's contribution to the total of Joelle's and Mary's contribution is 5 : 3. What is the total contribution by the four girls if Joelle's contribution is ¹₈ of Mary's contribution and the total amount contributed by Gillian and Kylie is $528?

Gillian	Joelle	Mary	Kylie	Total
3x6	4x6			7x6
	3x3		5x3
	1x1	8x1
18 u	1 u	8 u	15 u	42 u

Working backwards.

Total amount that Joelle and Mary had is the combined repeated identity.
LCM of 3 and 9 = 9

Total amount that Joelle, Mary and Kylie had is the next combined repeated identity.
LCM of 4 and 6 = 24 

Total amount contributed by Gillian and Kylie
= 18 u + 15 u
= 33 u

33 u = 528

3 u = 528 ÷ 33 = $16

Total contribution by the four girls
= 42 u
= 42 x 16
= $672

Answer(s): $672