Answer:
The simplest form will be 3:1
Step-by-step explanation:
Hey! You need to find the greatest common divisor of the two numbers in the ration (https://en.wikipedia.org/wiki/Greatest_common_divisor). It is 6 in this case. Then you divide both numbers in the ratio by the Greatest common divisor (6). So 18/6 = 3 ; 6/6 = 1. The simplest form will be 3:1
I hope that I have helped you! I will be really happy, If you mark my answer as Brainliest.
