There is 2n+150 litres of oil in total. We have to divide this oil into 3 equal parts which will be named Tank A, Tank B, Tank C.
C was empty at first, then it was delivered 500 litres in total. So if every tank was supposed to have one thirds of it, that means one thirds of the oil equals to 500 litres.
All of the oil would be 500x3=1500 litres
2n+150 was the formula to our total litre count, so if we make a connection between them, we can solve this question for the value of n.
2n+150=1500
2n=1350
n=675