## Geometry: Common Core (15th Edition)

$\angle 2$ is supplementary to $\angle 7$ because this is given. $\angle 2$ is supplementary to $\angle 3$ because of the definition of a linear pair. Because of the Congruent Supplements Theorem, $\angle 7\cong\angle 3$. Therefore, because of the Converse of the Corresponding Angles Theorem, $l\parallel m$.