4.
The angles ∠6 and ∠8 are congruent because they are alternate interior angles.
5.
The angles ∠4 and ∠5 added are equal to 180° because they are supplementary angles.
6.
If ∠1 is equal ∠7, then they are alternate exterior angles, therefore the lines p and q need to be parallel.
7.
The angles ∠1 and ∠2 are congruent because they are vertically opposite angles.
8.
If ∠2 and ∠6 are supplementary, they are consecutive interior angles, therefore the lines p and q need to be parallel.
9.
The angles ∠6 and ∠9 are congruent because they are corresponding angles.