a) Alternate interior angles are congruent where a transversal crosses parallel lines. The marked alternate interior angles are congruent, so the lines are parallel.
b) Corresponding angles are congruent where a transversal crosses parallel lines. The marked corresponding angles are not congruent, so the lines are not parallel.
a) Alternate interior angles are congruent where a transversal crosses parallel lines. The marked alternate interior angles are congruent, so the lines are parallel.
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b) Corresponding angles are congruent where a transversal crosses parallel lines. The marked corresponding angles are not congruent, so the lines are not parallel.
