Take out 3kg from A every day and put it in B bucket.
After 8 days, there is 3X-24 left in a barrel.
Kilograms of oil, barrel B has X+24 kilograms of oil. According to the fact that the oil in barrel B is twice as much as that in barrel A, the equation can be obtained.
2*(3x-24)=x+24
The solution is x= 14.6.
∴
A barrel oil is 43.8kg, and B barrel oil14.6kg..