Opal, Jaslyn, Julie and Jen jointly contributed to the cost of a present for their schoolmate. Opal's contribution is ¹₂ of the total contribution made by the four girls. The ratio of Jen's contribution to the total of Jaslyn's and Julie's contribution is 3 : 1. What is the total contribution by the four girls if Jaslyn's contribution is ¹₇ of Julie's contribution and the total amount contributed by Opal and Jen is $112?

Opal	Jaslyn	Julie	Jen	Total
1x32	1x32			2x32
	1x8		3x8
	1x1	7x1
32 u	1 u	7 u	24 u	64 u

Working backwards.

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

Total amount that Jaslyn, Julie and Jen had is the next combined repeated identity.
LCM of 1 and 32 = 32 

Total amount contributed by Opal and Jen
= 32 u + 24 u
= 56 u

56 u = 112

1 u = 112 ÷ 56 = $2

Total contribution by the four girls
= 64 u
= 64 x 2
= $128

Answer(s): $128