since it is a straight line at the top, those angles are going to add up to 180 degrees. The corners of a square is 90 degrees. And we know the other side is 45. 90 + 45 = 135 so 180 - 135 = 45 and that is the measure of the other angle. An easier way to do it would be that theres another square and the corners are still 90 degrees so you just do 90 - 45 and get 45 now you add the 45 to 90 and get 135 which is the answer.
