The difference between the bases is
cm. Consider the two heights (one is already drawn with a dashed line). They divide the trapezoid in three regions: two right triangles and a rectangle.
The right triangle has height
cm, and the base is half the difference between the bases, which is
cm. So, its area is
cm squared.
There are two of these triangles, so their area sum up to
cm squared.
Finally, the area of the rectangle is easy, since we know width and height:
So, the total area is
cm squared