Hello!
First you have to find angle 1
angle 1 and angle 4 are supplementary meaning they add to 180
angle 1 + angle 4 = 180
angle 1 + 150 = 180
angle 1 = 30
The angles in a triangle always add up to 180
angle 1 + angle 2 + angle 3 = 180
30 + 40 + angle 3 = 180
70 + angle 3 = 180
angle 3 = 110
The answer is 110°
Hope this helps!
