Answer:
20
Explanation:
We can quickly work this out by working backwards. If the difference was muliplied by 2 to get 24, there is only one number than can achieve this: 12. 12 x 2 = 24. Then because 8 was subtracted, we do the opposite and add it. 8+12=20
We can check this by starting with 20. If 8 was subtracted from 20 we get 12. Then if we multiply 12 by 2 we get 24. Therefore 20 is the correct answer.