The way I am doing it may not be the correct way but it works. What I did was take 90° away from 120° to make it 30° as if there is a line. I did this so I could make a triangle. Using the triangle addition postulate, I Added 30 to 80 to get 110 than subtracted that from 180 to get 70. Lastly, i added 90° to 70° to get 160°
