4) Angle a and 63 degrees are angles of a straight line. They are also called linear pairs. The sum of the angles on a straight line is 180 degrees. This means that
a + 63 = 180
a = 180 - 63
a = 117 degrees
angle b and 63 degrees are vertically opposite angles. Vertically opposite angles are equal. Thus,
angle b = 63 degrees
angle a and angle c are vertically opposite angles. thus,
angle c = 117 degrees
