A circle is centered at O. It contains has three points, P, A, and B on its boundary. The measure of angle APB is 20°. The angle from the center that intercepts the same arc AB measures x. From Euclidean geometry, we know that x=40°.

I looked it up, maybe, “Inscribed angles”? https://www.cliffsnotes.com/study-guides/geometry/circles/arcs-and-inscribed-angles heres a link to the math page I found with some terminology and it breaks it down a little bit. Hopefully someone can give us an exact answer! :)