PSLE
At first, Jeremy had some money. He spent ¹₄ of it on a vest and ²₅ of the remainder on a jacket. After that, his father gave him $320. The ratio of the total amount of money he had in the end to the amount of money he had at first was 5 : 4. How much money did Jeremy have at first?
Fraction of the total on remainder
= 1 - ¹₄
= ³₄

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

Fraction of the total on what was left
= ³₄ x ³₅
= ⁹₂₀

The total at first is the repeated identity.  Make the total at first the same. LCM of 4 and 20 = 20

Total in the end : Total at first
5_x5 : 4_x5
25 : 20

Amount that his father gave him
= 25 u - 9 u
= 16 u

16 u = 320

1 u = 320 ÷ 16 = 20

Amount that Jeremy had at first
= 20 u
= 20 x 20
= $400

Answer(s): $400