PSLE
Four girls, Nora, Diana, Natalie and Penelope raised money for a charity. Nora and Diana raised a total of $117. Together, Diana, Natalie and Penelope raised a total of $195. The total amount of money raised by all 4 girls is 3 times the amount that Diana raised. How much money did Diana raise?
Amount that Diana and Nora raised = $117
Amount that Diana, Natalie and Penelope raised = $195

Diana is the repeated identity.

Diana + Nora = 117 --- (1)
Diana + Natalie + Penelope = 195 --- (2)

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

(1) + (2)
(Diana + Nora) + (Diana + Natalie + Penelope) = 117 + 195
Diana + 4 girls = 312
1 u + 3 u = 312
4 u = 312

1 u = 312 ÷ 4 = 78

Amount that Diana raised
= 1 u
= $78

Answer(s): $78