The photo shows a portion of an airport. the measure of $\angle4$ is 84 $\degree$ . find the measure of $\angle6$ . two parallel lines, a and b are drawn on two parallel runways and a transverse is drawn on another runway, which intersect the parallel runways. angle 1 and angle 3 are linear angles. angle 1 and angle 4 are vertical angles. angle 3 and angle 2 are vertical angles. angle 4 and angle 8 are corresponding angles on the same side of the transversal. angle 2 and angle 6 are corresponding angles on the other side of the transversal. angle 6 and angle 7 are vertical angles. angle 8 and angle 5 are vertical angles. the measure of $\angle6$ is $\degree$ .