Use the site called Desmos, it's a graphing calculator and should help you in all the ways you need. It isn't complex. Just put that equation in a box and it graphs it for you.
There are 360 degrees so divide 360 by 20 and get 18 degrees
Yes; this is a linear function because you plug in a number and multiply it by two, so the function would be y=2x, which is linear despite the fact that it lacks a b value.
Hope this helps! :)
