Hi, in order to solve (a) we must first understand what a composite number is. A composite number is a positive integer which has more than 1 factor. In this case, the answer is 9, 6, 18 because 9 has factors of 1, 3, 9. 6 has factors 1, 2, 3, 6. And 9 × 6 = 54. 9 × 4= 36. 6 × 6 = 36. 18 × 3 = 54. 18 × 2 =36.

Hope this helps :))

How about...

...18 as a composite factor?

Ah yes 18 is acceptable too thanks for pointing out :))