1. All numbers are less than 20.

2. 1/4 of the numbers are multiples of 8.
You will need to find out how many numbers needed.

1/4 X 8 = 2 (so 2 numbers are needed.)

From 1 to 20, there are only 2 numbers that are multiples of 8.
They are 8 and 16.

3. 1/2 of the numbers are divisible by 3.
You will need to find out how many numbers are needed.

1/2 X 8 = 4 (so 4 numbers are needed.)

From 1 to 20, there are 6 numbers that can be divided by 3.

They are 3,6,9,12,15,18.

4. The rest of the numbers are factors of 12.
You will need to find out how many numbers are left.
8 - 2 - 4 = 2 (so 2 numbers are left.)

From 1 to 20, there are 6 numbers that are factors of 12.

They are 1,2,3,4,6,12.

You must remember that the question asked for 8 numbers, so you can't use the same answer for part 3 and 4.

The answer to this question is 2,3,4,6,8,9,12,16.

Let me know if you don't understand.