Answer:
5:6
Step-by-step explanation:
15 and 18 are both multiples of 3. 3 is their GCF(Greatest Common Factor). So, we can start by dividing them by 3. That gives us 5 and 6, so the simplest ratio of 15:18 is 5:6.
I hope this helps :) if so, brainliest would help me out a lot <3