Three tanks, a,b, c are used to store oil. tank a contains 'n' litres of oil. tank b contains (n+150) litres of oil. tank c is empty. oil is pumped from tank a and from tank b into tank c so that all three tanks contain the same amount of oil. 500 litres of oil are pumped from tank a into tank c. work out the value of 'n'.

Before Transferring oil to Tank C :
Tank A = n
Tank B = n + 150
Tank C = 0

Total = n + n + 150 
Total = 2n + 150

After transferring some oil to Tank C, each of the tank has the same amount.
Each tank = (2n + 150) ÷ 3 = 2/3 n + 50

500ml was transferred from tank A to Tank C:
n - (2/3n + 50) = 500
n - 2/3n - 50 = 500
1/3n = 550
n = 1650 ml


The value of n is 1650.


Check:
Before Transfer: 
Tank A = n = 1650
Tank B = n + 150 = 1650 + 150 = 1800
Tank C = 0

Total = 1650 + 1800 = 3450ml

After transfer:
Each tank = 3450 ÷ 3 
Each tank = 1150

Tank A before transfer = 1650
Tank A after transfer = 1150
1650 - 1150 = 500 (checked)