Same-side Interior Angles Theorem:
Angles on the same side are congruent.
Corresponding Angles Postulate:
This states that if a transversal cuts two parallel lines, the angles in the corresponding figure are congruent.
Substitution Property of Equality:
This states that if x=y, then x can be substituted for y in any equation.
Angle Congruence Postulate:
This states that if two angles in a figure are congruent, the rest in the figure is.
Transitive Property of Congruence:
If a=b and b=c, then a=c.
So,
I would say the Same Side Interior Angles Theorem for the first one.
Transitive Property for the Second.
Then angle congruence for the third.
Check my answers, because I never was good at proofs.
This took me forever, I'm sorry.