A is 30% more than B. So, A = B + 30% of B = B + 30/100 *B = B + 3/10 *B = 13/10 *B. B is 60% less than C. So, B = C - 60% of C = C - 60/100 *C = C - 3/5 *C = 2/5 *C.
The weight is proportional to the price. So if 10lb cost $18.24, quarter as much (2.5lb) would cost four times less($18.24÷4=$4.56).
So, Mr Yeo has 32 litres of water to begin, by taking away the 3/8 (12 litres) you get 20 litres, dividing that by 4 gives you 5litres.
Your answer is then 5 Litres