So you need to do a couple of steps here. These include finding the area of the whole rectangle, area of half of the circle, and then just subtracting the half circles area from the rectangles area to find our final answer:
To start, lets find the area of the whole rectangle disregarding whats shaded
Area (Rectangle):
A = bh
A = 20 x 14
A = 280 ft²
Now the half-circle:
Area of a circle is A = πr², for half-circle, just put that whole thing over 2
Our diameter is equal to the height of the rectangle, and the radius (r) is half of the diameter.
A = (πr²)/2
A = (π(7)²)/2
A = 76.96902001294993 ft²
And finally we just subtract the half circle's area from the rectangles area for the shaded area
A = 280 - 76.96902001294993
A = 203.0309799870501
round to 2 decimal places, your final answer is:
203.03