1. Geometry 3-3 Proving Lines Parallel
Use two different colors to mark all of the congruent angles.
These angles are only congruent because the lines are parallel

2. Determine if r || s.
m2 = (10x + 8)°,
m3 = (24x – 3)°, x = 5
m2 = 10(5) + 8 = 58°
m3 = 24(5) – 3 = 117°
58° + 117° = 175°
2 + 3 should equal 180, so r is not parallel to s

3. Determine if r || s.
m8 = (3x + 10)°,
m4 = (4x – 2)°, x = 12
m8 = 3(12) + 10 = 46°
m4 = 4(12) – 2 = 46°
8 + 4 should be equal, so r || s (r is parallel to s)

4. What value of x makes a || b?
140°
x = 180
16x + 148= 180
16x = 32
x = 2
(16x + 8)°