The Exterior Angle Theorem states the following:
An exterior angles measurement will always be equal to the sum of the two remote interior angles (the two angles not adjacent to the exterior angle). Using the diagram below, according to the Exterior Angle Theorem angle 1 + angle 2 = angle 4. As you can see in the picture on the right, angle 1 is 31 degrees and angle 2 is 44 degrees and using the Exterior Angle Theorem angle 4 would be 75 degrees because 31 + 44 = 75 .