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Answer:
m∠3 = 63°
Step-by-step explanation:
Where a transversal crosses parallel lines, all of the obtuse angles are congruent, and all of the acute angles are congruent. The obtuse and acute angles are supplementary.
Angle 1 is an obtuse angle; angle 3 is an acute angle.
angle 3 = 180° - angle 1 = 180° -117° = 63°
The measure of angle 3 is 63°.
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<em>Additional comment</em>
There are a number of applicable theorems describing the different angle relationships. Taken together, they are summarized by the first statement above. For example, we could declare angles 1 and 4 to be "corresponding" (hence, congruent), and angles 4 and 3 to be a "linear pair", hence supplementary. The net result is that angle 1 is supplementary to angle 3, as we said above.
We could also get there via relations between alternate exterior angles, alternate interior angles, consecutive exterior or interior angles, and other ways. While that terminology is useful to understand in some problems, it is largely irrelevant here.
