∠1 ≅ ∠3 . . . . vertical angles are congruent
∠3 ≅ ∠5 . . . . opposite angles of a parallelogram are congruent
∠1 ≅ ∠5 . . . . transitive property of congruence
∠5 ≅ ∠7 . . . . vertical angles are congruent
∠1 ≅ ∠7 . . . . transitive property of congruence
_____
You might be able to get there faster if additional angles were marked at the intersections near the labels b and m. Then you could use opposite exterior angles and corresponding angles, for example.
