Explanation:
the angles at an intersection point of 2 lines are the same on either side of one of the lines. they are just left-right mirrored.
and all the intersection angles at parallel lines are the same, as each parallel line represents the same attributes (except for the exact location) as the other parallel lines. otherwise they would not be parallel.
that all means for our case that
angle 7 = 6x + 163 = angle 2 = -6x - 5
and so, we can solve for the variable expressions :
6x + 163 = -6x - 5
12x + 163 = -5
12x = -168
x = -168/12 = -14
therefore
angle 7 = 6x + 163 = 6×-14 + 163 = -84 + 163 = 79°