Question

drum of kerosene oil is 3 by 4 full when 15 litres of oil is drawn from it it is 7 by 12 full the capacity of the drum is

Answer 1

Let the capacity of the drum be x litres so , when the drum of oil is 3 ths full , it is 3 by 4 x when you remove 15 litres of oil ( 3 by 4 x 15) 7 by 12 ths of the capacity remains ( 7 by 12 x ) write this equation as
3 by 4 x - 15 =7 by 12 x
Isolate the variable
3 by 4 x - 3 by 4 x -15=7 by 12 x - 3 by 4 x -15 =1 by 6 x
-15 (-6)=-1 by 6 x (-6)
X= 90