Question

Help with number 4 please?

Answer 1

10 because 7 x 3 = 21 and 7 + 3 = 10 so your answer is 10

Answer 2

The only factors of 21 are: 1 and 21 or 3 and 7.

Since the two number mentioned are single digits, the numbers being used must be 3 and 7.

To get the sum, just add them together!
3 + 7 = 10

The answer to your problem is 10.

Hope this helps!!