721.64 mi^2
Explanation:
Area of the large rectangle A2 is
A2 = (32.7 mi)(26.3 mi) = 860.01 mi^2
Area of the small rectangle A1 is
A1 = (10.1 mi)(13.7 mi) = 138.37 mi^2
Therefore, the area of the shaded region is simply the difference between A2 and A1:
Area (shaded) = A2 - A1
= 860.01 mi^2 - 138.37 mi^2
= 721.64 mi^2