Given: angle 3 and angle 5 are supplementary prove: line l is parallel to line m
1 / 2
/ the transversal should be a diagonal
3/4
/
5 / 6
/
7/8

Since line l and line m are cut by the transversal and angle 3 and 5 are supplementary, that means they are consecutive interior angles which proves that the two lines are parallel.

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