PSLE
At first, Vincent had some money. He spent ¹₃ of it on a blazer and ²₃ of the remainder on a shirt. After that, his uncle gave him $280. The ratio of the total amount of money he had in the end to the amount of money he had at first was 4 : 3. How much money did Vincent have at first?
Fraction of the total on remainder
= 1 - ¹₃
= ²₃

Fraction of the remainder on what was left 
= 1 - ²₃
= ¹₃

Fraction of the total on what was left
= ²₃ x ¹₃
= ²₉

The total at first is the repeated identity.  Make the total at first the same. LCM of 3 and 9 = 9

Total in the end : Total at first
4_x3 : 3_x3
12 : 9

Amount that his uncle gave him
= 12 u - 2 u
= 10 u

10 u = 280

1 u = 280 ÷ 10 = 28

Amount that Vincent had at first
= 9 u
= 9 x 28
= $252

Answer(s): $252