3. Eight is subtracted from a number, and then the difference is multiplied by 2. The result is 24. Find the number.

20

Step-by-step 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.