Two numbers are between 10 and 20. Their greatest common factor is 3. Which two numbers could they be?

12 and 15 or

12 and 18 or

15 or 18

Step-by-step explanation:

The two numbers have to both be divisible by 3, since their greatest common factor is 3. This only leaves ...

12, 15, or 18 (no other numbers between 10 and 20 are divisible by 3)

The factors of 12 are: 2, 3, 4, 6, and 12

The factors of 15 are: 3, 5, and 15

The factors of 18 are: 2, 3, 6, 9, and 18

All three numbers have 3 as a greatest common factor, so we have 3 pairs of numbers they could be ...

12 and 15 or

12 and 18 or

15 or 18