hi can someone help I’m doing ixl AND I DONT UNDERSTAND ILL GIVE BRAINLIESST please explain

Answer:
5:9
Step-by-step explanation:
the circumference is d*pi
so you must find the diameter of both circles
31/pi = 9.86760647
which is about 10
57/pi = 18.1436635
which is about 18
10:18 is your ratio
but you can simplify this down to
5:9