PSLE
Four girls, Joelle, Linda, Risa and Penelope raised money for a charity. Joelle and Linda raised a total of $107. Together, Linda, Risa and Penelope raised a total of $378. The total amount of money raised by all 4 girls is 4 times the amount that Linda raised. How much money did Risa and Penelope raise?
Amount that Linda and Joelle raised = $107
Amount that Linda, Risa and Penelope raised = $378

Linda is the repeated identity.

Linda + Joelle = 107 --- (1)
Linda + Risa + Penelope = 378 --- (2)

Amount that Linda raised = 1 u
Amount that 4 girls raised = 4 u

(1) + (2)
(Linda + Joelle) + (Linda + Risa + Penelope) = 107 + 378
Linda + 4 girls = 485
1 u + 4 u = 485
5 u = 485

1 u = 485 ÷ 5 = 97

Total amount that Risa and Penelope raised
= 378 - 1 u
= 378 - 97
= $281

Answer(s): $281