One way is to find the area of the shape as if it was a whole square instead of an H shape.
That is (125+75+125) x (345), which is 112125 ft^2.
From this, let's subtract the areas of the cut-outs.
The cutouts are squares and both the same size. One side of it is 112 feet, so the area of one is 112x112=12544. So, the two squares have an area of 25088.
Now subtract that from the original total. 112125-25088=87037. <<that is the area.
You might want to double check my work.