In the figure shown, line c intersects parallel lines s and t. What is the value of x ?

Explanation

The correct answer is 70. Based on the figure, the angle with measure 110o and the angle vertical to the angle with measure xo are same side interior angles. Since vertical angles are congruent, the angle vertical to the angle with measure xo also has measure xo . It's given that lines s and t are parallel. Therefore, same side interior angles between lines s and t are supplementary. It follows that x = 110 + 180. Subtracting 110 from both sides of this equation yields x = 70.