Final answer:
The theorem that justifies each of the given if-then statements is the Parallel Lines and Transversals Theorem. According to this theorem, if two parallel lines are cut by a transversal, then the corresponding angles are congruent.
Step-by-step explanation:
The theorem that justifies each of the given if-then statements is the Parallel Lines and Transversals Theorem. According to this theorem, if two parallel lines are cut by a transversal, then the corresponding angles are congruent. In the given statements:
- If line p is parallel to line r, then angle 22 is congruent to angle 27.
- If line p is parallel to line r, then angle 24 is congruent to angle 25.
- If angle 23 is congruent to angle 26, then line p is parallel to line r.
- If line p is parallel to line r, then angle 21 is congruent to angle 25.
- If line p is parallel to line r, then the sum of angle 24 and angle 26 is 180 degrees.
- If line p is parallel to line r, then the sum of angle 2 and angle 27 is 180 degrees.