If I understand this question correctly, the angle of reflection should be 30 degrees with respect to the mirror as well. The angle of the incoming ray and the angle of the ray that is reflected will always be the same.
The ray that is coming in is called the indcident ray and the angle that it makes with an imaginary line perpendicular to the surface of the mirror is called the angle of incidence. The angle of incidence and the angle of reflection are always the same. (This is true as long as the mirror is flat.)
Angle of reflection is the angle that a reflected ray of light makes with the normal to the reflecting surface. The normal is an imaginary line which is perpendicular to the reflecting surface.
The angle of reflection is always equal to the the angle of incidence, which is the angle that the incoming ray, called incident ray makes with the normal.
(Please note that the angle of incidence and angle of reflection are always defined in terms of angle the ray makes with the normal. There is nothing like "angle of reflection with respect to mirror)
The angle of incidence can be calculated from the angle incident rays makes the reflection surface as:
Angle of incidence = 90 - Angle made with reflecting surface
The angle with the reflecting surface, that is mirror, is given as 30 degrees.
Angle of incidence = 90 - 30 = 60 degrees
Angle of reflection = angle of incidence = 60 degrees
According to the law of reflection in a plane mirror, incident , the point of pncidence of the incident ray on the surface of the mirror , the normal drawn to the surface of the mirror at the point of incdence and the reflected ray from the mirror are all lying inthe same plane. Also the angle incident ray makes with the normal is equal to the angle the reflected ray make with the normal.
If IO is the incident ray, ON is the normal at the point of incidence, and OR, is the reflected ray, then , IO,ON and OR are all in the same plane.
Also, angle ION is the angle of incidence.
NOR is the angle of reflection,
Then angle ION = angle NOR.
In this case angle IOR = 90-30 =60.
Therefore angle of reflection = NOR = 60 degree.
angle of reflection will be 30°. the angle of incidence and angle of reflection is always equal in case of a plane mirror .