The reference angle is the angle that always uses the x-axis as a frame of reference. The reference angle is the smallest angle between the terminal side and the x-axis.
In the 1 st Quadrant: reference angle is the same ( x ).
In the 2nd Quadrant: 180° - x.
In the 3rd Quadrant: x - 180°.
In the 4th Quadrant: 360° + x.
An angle that measures 305° is in the 4th Quadrant:
360° - 305° = 55°
Answer: the reference angle is 55°.