Answer:
2a^2b
Explanation:
(tried my best but can't be sure I remember how to do it correctly)
First, you find the GCF of 18 and 20, which is 2.
18 > 2 * 3 * 3
20 > 2 * 2 * 5
The next part is where I'm a little hesitant. I say there is an 'a' for each number and only one 'b', so we forget about the 'b' and write 'a^2.'