PLS IL MAKE U THE BRAINLIEST NEED HELP WITH THIS PLEASE Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles.
In the diagram below, line a and line b are parallel, line c is a transversal, and the measure of ∠ 1 is 100°.

Is ∠3 congruent to ∠ 1? On the lines below, how you determined your answer. If it is not congruent, give the correct measure of ∠ 3.