Ineed . angle a and angle b are supplementary angles. what must be true about the angles? a: the angles were formed by two intersecting lines and are on opposite sides. b: the sum of the angles is 180°. c: the sum of the angles is 90°. d: the angles share a common side and vertex.

With these transversals across parallel lines the angles are either congruent or supplementary (adding to 180) and its pretty easy to figure out which is which, obtuse verse acute in the figure.

Each yellow circle indicates x and the path to the next square.  So for example the Start has alternate interior angles, which are congruent, so x is 141 degrees.