Question

what number is a factor of 15 but not a multiple of 3?

Answer 1

5 is a factor of 15 without being a multiple of 3

Answer 2

15 has a few factors; list them out: 1, 3, 5, 15. 15 and 3 are both divisible by 3 (so they're multiples of 3) but 1 and 15 aren't.