Idon't know how to do this! use the guide to construct a two column proof proving that lines l and m are parallel. angles 1 and 2 are supplementary by definition.

Reasons:
2) Same-Side Interior Angles Theorem
4)Definition of Supplementary Angles
5)Transitive Property of Congruence
6)Subtraction Property of Congruence
Statements:
4)m<1+m<3=180
6)m<2=m<3
7)Alternate Interior Angles Converse Theorem
You're welcome

2. Def of Supplementary Angles
4.
  A.m∠1+m∠3=180°
  B.Def of Supplementary Angles
5.Transitive Prop
6.
A.∠3≅∠4
B.same side interior angles theorem
7.Def of parallel line