We are given that line p is parallel to line q, which means angle 9 = angle 6 as they are alternate interior angles.
So angle 6 is 110 degrees. But this clashes with angle 8 being different at 70 degrees. Angles 6 and 8 must be congruent if we wanted lines 'a' and b to be parallel. Angles 6 and 8 are corresponding angles.
