Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
3. Proofs with Parallel Lines
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Exercise 7 Page 142

Use the Consecutive Interior Angles Converse.

x=60

Practice makes perfect
Both angles are between the lines and on the same side of the transversal. Therefore, the angles can be classified as consecutive interior angles. According to the Consecutive Interior Angles Converse, if the angles are supplementary, the lines are parallel. We can therefore write the equation x+2x=180. Let's solve this equation.
x + 2 x = 180
3 x = 180
x = 60
When x=60, m ∥ n.