Ok, so
We want to write the size of each angles:
Remember that 105° and z are supplementary angles. So, we can write:

Notice that both lines are parallel. So,

Now, as you can see, the vertical lines and the horizontal lines are parallel, then, we can say that the figure is a parallelogram.
For this reason, remember that, in a parallelogram:
Two pairs of angles are the same, and the sum of all internal angles in a parallelogram is always 360°.
Therefore,

Then,
