Question

Given the following information, determine which lines, if any, are parallel. State the

postulate or theorem that justifies your answer.

Answer 1

parallel lines a and b

parallel lines l and m

Explanation:

25 A.

Angles 3 and 7 are alternate interior angles of lines a and b cut by transversal l.

Since angles 3 and 7 are congruent, lines a and b are parallel by the theorem:

If two lines are cut by a transversal such that alternate interior angles are congruent, then the lines are parallel.

25 B.

Angles 5 and 12 are same side interior angles of lines l and m and transversal b.

Since the sum of the measures of the angles 5 and 12 is 180, then angles 5 and 12 are supplementary angles making lines l and m parallel by the theorem:

If two lines are cut by a transversal such that same side interior angles are supplementary, then the lines are parallel.