Given ,

In parallelogram ABCD,

∠DAB = 75°

∠DBC = 60°

∵ ∠DAB= ∠BCD [opposite angles of parallelogram]

∠BCD = 75°

Now in ∆BDC

= ∠DBC+∠BDC+∠BCD = 180°

= 60°+∠BDC+75° = 180°

=∠BDC = 180° - 135°

=∠BDC = 45°.