reference angle = $30^o$ Refer to the image below for the drawing.
Work Step by Step
The angle is positive so from the positive x-axis, move 150 degrees counterclockwise. (refer to the attached image in the answer part above) The reference angle of an angle is the smallest acute angle that the angle's terminal side makes with the x-axis. Thus, the reference angle of the given angle is: $=180^o - 150^o \\=30^o$