Answer:
D. 285
Step-by-step explanation:
Since all angles must add up to 360, if I haven't lost any brain cells, the last angle would need to be 285 degrees.
105 degrees
The angles in a triangle add up to 180 degrees. You know 2 of the sides, which are 55 degrees, and 20 degrees. You add them together, and you get 75 degrees. Do 180-75 to get 105, or the missing angle.
