Parallel lines have alternate interior angles that are equal, so angle 4 equals angle 2 and angle 1 equals angle 3. Vertically opposite angles are also equal, as are angles that are in a straight line, which add up to 180 degrees. Angles around a point also add up to 360 degrees.

1. ANGLEPROPERTIES OFPARALLELLINES

2. ALTERNATE ANGLES ARE EQUAL (Z)
angle 4 = angle 2 (alternate angles are equal)
angle 1 =angle 3 (alternate angles are equal)

3. REVIEW ANGLE PROPERTIES BETWEEN LINES
Vertically Opposite Angles are equal
b = 40
a = c

4. Angles are a point add up to 360
ANGLES IN A STRAIGHT LINE ADD UP 180