PSLE
Four girls, Mary, Pamela, Olivia and Gem raised money for a charity. Mary and Pamela raised a total of $142. Together, Pamela, Olivia and Gem raised a total of $212. The total amount of money raised by all 4 girls is 5 times the amount that Pamela raised. How much money did Mary raise?
Amount that Pamela and Mary raised = $142
Amount that Pamela, Olivia and Gem raised = $212

Pamela is the repeated identity.

Pamela + Mary = 142 --- (1)
Pamela + Olivia + Gem = 212 --- (2)

Amount that Pamela raised = 1 u
Amount that 4 girls raised = 5 u

(1) + (2)
(Pamela + Mary) + (Pamela + Olivia + Gem) = 142 + 212
Pamela + 4 girls = 354
1 u + 5 u = 354
6 u = 354

1 u = 354 ÷ 6 = 59

Amount that Mary raised
= 142 - 1 u
= 142 - 59
= $83

Answer(s): $83