PSLE
At first, Riordan had some money. He spent ¹₅ of it on a blazer and ²₅ of the remainder on a blouse. After that, his uncle gave him $180. The ratio of the total amount of money he had in the end to the amount of money he had at first was 6 : 5. How much money did Riordan have at first?
Fraction of the total on remainder
= 1 - ¹₅
= ⁴₅

Fraction of the remainder on what was left 
= 1 - ²₅
= ³₅

Fraction of the total on what was left
= ⁴₅ x ³₅
= ¹²₂₅

The total at first is the repeated identity.  Make the total at first the same. LCM of 5 and 25 = 25

Total in the end : Total at first
6_x5 : 5_x5
30 : 25

Amount that his uncle gave him
= 30 u - 12 u
= 18 u

18 u = 180

1 u = 180 ÷ 18 = 10

Amount that Riordan had at first
= 25 u
= 25 x 10
= $250

Answer(s): $250