Referring to the figure, find the unknown measure of angle ABC.

We know that for any inscribed angle on a cricle we have that:
[tex]m\angle ABC=\frac{1}{2}m\hat{AC}[/tex]Then in this case we have:
[tex]m\angle ABC=\frac{1}{2}(200)=100[/tex]Therefore the angle ABC is 100°