Please experts answer this.

Dear Student, 

 150° is the answer.

Given:
Angle of incident ray with the mirror = 15°
Therefore,
Angle of incidence = Angle of incident ray with the normal
                                    = 90° $-$ 15°
                                    = 75°
We know that angle of reflection is always equal to angle of incidence. Therefore, we have:
Angle of reflection = Angle of reflected ray with the normal = 75°
Hence, angle between the reflected and incident rays = 75° + 75° = 150°

Regards