The value of x = 135 degrees.
You can figure this out easily by extending the top and bottom sides of the trapezoid, and finding supplementary / corresponding angles.
First, look at the top. We know that supplementary angles add up to 180 degrees (or form a straight line), so subtract 180 - 45 to get 135 degrees.
When you extend the short (bottom) side of the trapezoid along with the long (top) side and the diagonal line, it’s easy to see that there are corresponding angles. The 135-degree angle corresponds with angle x, so the measure of x would therefore be 135 degrees.