The given angle is 75 degrees. The four angles together make up 360 degrees because quadrilaterals have a measurement of 360 degrees on the inside. The angle that is 75 degrees and angle 2 are opposites (I forgot the math word, sorry) so they are the same degrees. So we know that angle 2 is 75 degrees. Angles 1 and 2 are vertical pairs, as well as the given angle and angle 3. We know that vertical pairs equal 180 degrees. 180 - 75 = 105 degrees. Now we know that both angle 1 and 3 are 105 degrees. You could also find the measurment of angle 1 and 3 by making an equation.
