The angles 4 and 8 are alternate exterior angles. If x=5, this angles are:
[tex]\measuredangle4=13(5)-4=61[/tex][tex]\measuredangle8=9(5)+16=61[/tex]
Since the angles are equal, we conclude that the lines r ans s are parallel. This follows from the theorem: If two lines are cut by a transversal so that alternate exterior angles are congruent, then these lines are parallel.
