A reference angle of any angle is the acute angle from the terminal side of the angle to the x axis.
First find the reference angle for 168 degrees.
Since it is in the 2nd quadrant it is 180 - 168 = 12 degrees
The angle in the 1st quadrant with the same reference angle is 12 degrees.
The angle in the 2nd quadrant is just the angle you were given (168 degrees).
The angle in the 3rd quadrant is just 180 + 12 = 192 degrees.
The angle in the 4th quadrant is 360 - 12 = 348 degrees.