Because line a is parallel to line b
Angle 6 would be the same angle as angle 2, which is 78 degrees.
Angle 5 is a Supplementary angle to angle 6, which means angle 5 added to angle 6 must equal 180 degrees.
To find angle 5, subtract angle 6 from 180:
Angle 5 = 180 - 78 = 102 degrees.
