PSLE
Four girls, Dana, Zoe, Irene and Mary raised money for a charity. Dana and Zoe raised a total of $120. Together, Zoe, Irene and Mary raised a total of $264. The total amount of money raised by all 4 girls is 3 times the amount that Zoe raised. How much money did Dana raise?
Amount that Zoe and Dana raised = $120
Amount that Zoe, Irene and Mary raised = $264

Zoe is the repeated identity.

Zoe + Dana = 120 --- (1)
Zoe + Irene + Mary = 264 --- (2)

Amount that Zoe raised = 1 u
Amount that 4 girls raised = 3 u

(1) + (2)
(Zoe + Dana) + (Zoe + Irene + Mary) = 120 + 264
Zoe + 4 girls = 384
1 u + 3 u = 384
4 u = 384

1 u = 384 ÷ 4 = 96

Amount that Dana raised
= 120 - 1 u
= 120 - 96
= $24

Answer(s): $24