The shaded area is equal to the area of the circle substracted fromt he area of the trapezoid:

Area of a trapezoid:

a is long base
b is short base
h is height
Area of a circle:

The given trapezoid has a height equal to 2 times the radius of the circle in it. Then, the area of the shaded area is:

a=13in
b=9in
r=3in
