Explanation:
We know that:


.; because they are opposite angles.- Also,
; because they are alternate interior angles. - We can see that
; because they are supplementary angles and they are on a straight angle.
So, based on those deductions:

Then,

All these angles are the same, because they are opposite (1 and 3), alternate interior (5 and 5), and opposite (5 and 7).
Therefore,
