The sum of interior angles in a triangle is equal to 180 so to find angle 3:
180 - (52+25) = 103
B)
Angle 3 and angle 4 are supplementary so the measure of angle 4:
180 - 103 = 77
C)
Angle 1 and angle 2 and angle 3 are the interior angles of the triangle and their sum is 180 so is the sum of angle 3 and angle 4
D)
<u><em>The sum of two interior angles in a triangle is equal to an exterior angle that is supplementary to the third interior angle so the sum of angle 1 and angle 2 is equal to angle 4</em></u>
