Answer:
AHH! Geometry!
Thanks!
The arc has a length of 1/3
Step-by-step explanation:
So you first start off with this:

This is because a circle is 360 degrees, and we are talking about a 20 degree arc.
Simplifying, we get 
So then, you multiply the circumference with this "factor"

Hope this helps!
P.S. Stay Safe during quarantine!