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Practice 3-2	Proving Lines Parallel

1. Developing Proof Complete the paragraph proof for the figure shown.

Given:  and  are supplementary.
 and  are supplementary.
Prove: 

Proof Because  and  are supplementary,  and  are a. __?__ angles. By the Same-Side Interior Angles Theorem, b. __?__  c. __?__. Because  and  are supplementary,  and  are d. __?__ angles. By the  e. __?__ Theorem, . Because  and  both are parallel to f. __?__,  by Theorem g. __?__.

Which lines or segments are parallel? Justify your answer with a theorem or postulate.

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Algebra Find the value of x for which .

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