#### Answer

1. Given
2. substitution
3. $\overline{BC}$ $\parallel$ $\overline{DE}$

#### Work Step by Step

1. Given statements are always given to start a proof.
2. Substitution states as long as there is 1 variable in common in both statements, you an take that variable out and replace it with another. 3. By the definition of corresponding angles, we can prove the two lines are parallel because the two angles are cut by a traversal forming corresponding angles.