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Consider quadrilateral DECF.
As for any quadrilateral, the sum of its interior angles is 360°.
The angles D and C of this quadrilaterals are right angles;
their sum is 90° + 90° = 180°.
Hence, the sum of angles F and E of this quadrilateral is 360° - 180° = 180°.
Thus the angle CFD is the supplementary angle to angle E: ∠CFD = 180° - 57° = 123°.
But the angle BFD is the supplementary angle to the angle CFD.
So, we conclude that ∠BFD = 180° - 123° = 57°.
ANSWER. ∠BFD = 57°.
Solved.
