Answer
a) same-side interior angles theorem
b) same-side interior angles theorem
c) congruent supplements theorem
Work Step by Step
a) $\angle 3$ and $\angle2$ are same-side interior angles
b)$\angle 1$ and $\angle2$ same-side interior angles
c) Since $\angle 1$ and $\angle3$ have the same supplement, they are congruent.