Can’t find an answer to this! someone pls ! 4n+6n-2 = 2(n+3)

Which undefined geometric term is described as a location on a coordinate plane that is designed by an ordered pair (x, y) ?

Find the measure of the interior angles of the following regular polygons: a triangle, a quadrilateral, a pentagon, an octagon, a decagon, a 30-gon, a 50-gon, and a 100-gon.

Solve the triangle. a = 21°, c = 105°, c = 5