Nora, Betty, Rachel and Gabby jointly contributed to the cost of a present for their colleague. Nora's contribution is ¹₂ of the total contribution made by the four girls. The ratio of Gabby's contribution to the total of Betty's and Rachel's contribution is 5 : 1. What is the total contribution by the four girls if Betty's contribution is ¹₇ of Rachel's contribution and the total amount contributed by Nora and Gabby is $1320?

Nora	Betty	Rachel	Gabby	Total
1x48	1x48			2x48
	1x8		5x8
	1x1	7x1
48 u	1 u	7 u	40 u	96 u

Working backwards.

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

Total amount that Betty, Rachel and Gabby had is the next combined repeated identity.
LCM of 1 and 48 = 48 

Total amount contributed by Nora and Gabby
= 48 u + 40 u
= 88 u

88 u = 1320

1 u = 1320 ÷ 88 = $15

Total contribution by the four girls
= 96 u
= 96 x 15
= $1440

Answer(s): $1440