Alright, so you're looking for the GCF.
Greatest Common Factor
I don't wanna go into detail of what that is (if you don't already know what it is, please watch a video on what it is and how to find it.)
Our numbers are 18, 36, 54
What is the gcf of these numbers? They all are both divisble by 18 and that's the largest 18 can go, so 18 is the GCF.
18 is the answer.
