Angle 4 is an exterior angle which corresponds to the remote interior angles of 33 degrees and 75 degrees. Through the remote interior angle theorem, we can add the remote interior angles to get the exterior angle So we simply add 33 and 75 to get 33+75 = 108 If you chose not to use this theorem, then you can find angle three by using the fact that all three angles of the triangle must add to 180 degrees. So, 33+75+(angle 3) = 180 108+(angle 3) = 180 108+(angle 3) - 108 = 180 - 108 angle 3 = 72 degrees Then use the fact that angle 3 and angle 4 are supplementary (angle 3) + (angle 4) = 180 72 + (angle 4) = 180 72 + (angle 4) - 72 = 180 - 72 angle 4 = 108 degrees either way, we get the same answ
