Answer: 2 is the greatest common divisor.
Explanation:
Though they both have different multiplies 2 is the only number that shows up in both of those
18- 1, 2, 3, 6, 9, 18 are the multiple
16- 1, 2, 4, 8, 16, x, 2x, 4x, 8x, 16x are the multiple
Of those multiple 2 is the only number they both have in common
Therefore, 2 is the greatest common divisor
