Given the point (-8, -20), the terminal side of the angle (θ) is in the third quadrant, and the total angle in degrees is 180 + Φ, where Φ is the angle from the negative x-axis to the terminal side of θ.
Find Φ by using the x and y values given to form a right triangle with the hypotenuse being the terminal side of θ:
tan(Φ) = 20/8
Φ = tan-1(20/8) = 68.2°
θ = 180 + Φ = 248.2°