In a parallelogram, consecutive angles are supplementary angles.
On the other hand, since Y is supplementary to X, as well as W is supplementary to X, then Y and W have the same measure.
Additionally, since the segments WX and VY are parallel and the angles WXV and YVX are alternate interior angles, then the measure of YVX is the same as the measure of WXV.
Finally, since WV and XY are opposite sides of a parallelogram, their measures are the same. Then:

Therefore:
