Which of the following compound inequalities represents the graph on the number line below?
- x + 6 > 8 or 4x + 7 > - 9
X – 2 <0 or x + 8 > - 4
3x +1 < - 5 or x – 5 > - 1
- 2x - 2 < 2 or 3x > 12

We can prove this by doing a statement and reason (more or less). The first thing we need to do is a construction of segment OG which is parallel to BC and touches A. Since it forms a straight line, we can say that m<OAB + m<A + m<GAC is equal to 180° (because it is a straight line). But, by alternate interior angles theorem, we can say that m<B = m<OAB and m<C = m<GAC. Therefore, by transitivity, m<A + m<B + m<C = 180°. Since angles A, B, and C are the interior angles of triangle ABC, we proved that the sum of the interior angles of ABC is 180°.