Answer:
These kind of problems are super difficult Anna, don't feel bad for not getting this. there is a bunch of "implied" ideas here... i'll go over them below, maybe it will seem a bit easier. if not, ask some more questions in the comments of this problem , I'll see the comments and answer your question
Explanation:
the 1st implied idea is that there is 360 ° in a circle
next you have to know, that the angle x is also matched on the interior of the circle where the line of the angle x, first touches the circle. if that is confusing , don't worry i'll make a rough drawing to show you.
so we can know that the arc from the point where the angle x makes the tanget.. or just touches the circle to where it's other leg crosses the circle the 1st time, that's angle is equal to the arc that is left over from the total circle. see this is very "implied" nobody said.. by the way... it's 360 ° minus the other arcs.. well.. I just did.. but you had to come up with that on your own, before I said that.
x = left over arc
360 = 200 + 40 + x
120 = x