PSLE
Four girls, Zoe, Jaslyn, Sarah and Risa raised money for a charity. Zoe and Jaslyn raised a total of $73. Together, Jaslyn, Sarah and Risa raised a total of $155. The total amount of money raised by all 4 girls is 3 times the amount that Jaslyn raised. How much money did Sarah and Risa raise?
Amount that Jaslyn and Zoe raised = $73
Amount that Jaslyn, Sarah and Risa raised = $155

Jaslyn is the repeated identity.

Jaslyn + Zoe = 73 --- (1)
Jaslyn + Sarah + Risa = 155 --- (2)

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

(1) + (2)
(Jaslyn + Zoe) + (Jaslyn + Sarah + Risa) = 73 + 155
Jaslyn + 4 girls = 228
1 u + 3 u = 228
4 u = 228

1 u = 228 ÷ 4 = 57

Total amount that Sarah and Risa raised
= 155 - 1 u
= 155 - 57
= $98

Answer(s): $98