I'm happy to answer your question. If you have any questions, please ask. I hope to be your satisfactory answer O (∩ _ ∩) O.

Judging from the meaning of the question, ∠DAB=α, ∠ dad' = β;

∵△ABC?△BAD '

∴∠ Dabu = ∠ ABC; That is, α+β = ∠ ABC; ( 1)

∵ Quadrilateral ABCD is a parallelogram (or AD//BC).

∴ ∠ABC+∠DAB= 180？ (2)

Substitute (1) into (2) to get α+β+α= 180?

∴β= 180? -2α