In order to find an angle in a triangle we need to know the other two angles, because the angles in a triangle all add up to 180 degrees. So, knowing two will get us the other one. In this case, we know two angles. One of them is 55, and the other, since it is a right triangle, is 90. So the two angles we know are 55 and 90. Using that all angles in a triangle add up to 180, we can use
