Which statement is used to prove that angle PTR is always equal to angle STQ?
Lines PQ and RS do not have a fixed length.
Angle PTR and angle PTS are supplementary angles.
Lines PQ and RS intersect at an angle less than a right angle.
Angle PTR and angle PTS are complementary angles.
PQ and RS are two lines that intersect at point T.

Yeah. I would say Angle PTR and angle PTS are supplementary angles. is the answer because when thinking of proving vertical angles congruent, you'd need to use supplementary angles and the transitive property at the very least.