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Answer:
∠B = ∠C = 138°
∠D = 42°
Step-by-step explanation:
Angles between the parallel bases are supplementary:
∠B = 180° -∠A = 180° -42° = 138°
Right-side angles are the same measure as their mirrors across the line of symmetry.
∠C = ∠B = 138°
∠D = ∠A = 42°
