Ivory, Anna, Cindy and Tina jointly contributed to the cost of a present for their sister. Ivory's contribution is ¹₂ of the total contribution made by the four girls. The ratio of Tina's contribution to the total of Anna's and Cindy's contribution is 5 : 3. What is the total contribution by the four girls if Anna's contribution is ¹₃ of Cindy's contribution and the total amount contributed by Ivory and Tina is $936?

Ivory	Anna	Cindy	Tina	Total
1x32	1x32			2x32
	3x4		5x4
	1x3	3x3
32 u	3 u	9 u	20 u	64 u

Working backwards.

Total amount that Anna and Cindy had is the combined repeated identity.
LCM of 3 and 4 = 12

Total amount that Anna, Cindy and Tina had is the next combined repeated identity.
LCM of 1 and 32 = 32 

Total amount contributed by Ivory and Tina
= 32 u + 20 u
= 52 u

52 u = 936

3 u = 936 ÷ 52 = $18

Total contribution by the four girls
= 64 u
= 64 x 18
= $1152

Answer(s): $1152