write all the factors of 18. use commas to separate them.

Explanation:

Step1: Recall factor - definition

A factor of a number divides the number evenly.

Step2: Start from 1

$1\times18 = 18$, so 1 and 18 are factors.

Step3: Consider 2

$2\times9=18$, so 2 and 9 are factors.

Step4: Consider 3

$3\times6 = 18$, so 3 and 6 are factors.

Answer:

1, 2, 3, 6, 9, 18