Risa, Rachel, Hilda and Gabby jointly contributed to the cost of a present for their colleague. Risa's contribution is ⁵₈ of the total contribution made by the four girls. The ratio of Gabby's contribution to the total of Rachel's and Hilda's contribution is 5 : 1. What is the total contribution by the four girls if Rachel's contribution is ¹₇ of Hilda's contribution and the total amount contributed by Risa and Gabby is $2280?

Risa	Rachel	Hilda	Gabby	Total
5x16	3x16			8x16
	1x8		5x8
	1x1	7x1
80 u	1 u	7 u	40 u	128 u

Working backwards.

Total amount that Rachel and Hilda had is the combined repeated identity.
LCM of 1 and 8 = 8

Total amount that Rachel, Hilda and Gabby had is the next combined repeated identity.
LCM of 3 and 16 = 48 

Total amount contributed by Risa and Gabby
= 80 u + 40 u
= 120 u

120 u = 2280

1 u = 2280 ÷ 120 = $19

Total contribution by the four girls
= 128 u
= 128 x 19
= $2432

Answer(s): $2432