Answer:
150 D
Explanation:
In a triangle the interior angles must add up to 180, so to find angle 1 you must subtract angles 2 and 3 from 180:
180-100 = 80
80-50 = 30
So the measure of angle 1 is 30. Now because we know that a straight line is 180 degrees, we know that if there is a line connected to it, the angles that it forms must add back up to 180. So we would subtract angle 1 from 180 to get angle 4:
180-30 = 150
That is why 150 or D is your answer.
Hope this helps!
