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Answer:
(a) 103°
Explanation:
The trapezoid is isosceles, so left-side angles are congruent to right-side angles. That is, ∠2≅∠3.
Each side of the trapezoid is a transversal between two parallel lines. The interior angles of the trapezoid are "consecutive interior angles", so are supplementary.
∠2 = ∠3 = 180° -77° = 103°