The left side is a half circle.
The area of a circle is PI x r^2
The diameter of the circle would be the height of the rectangle, given as 10 feet.
The radius is 1/2 the diameter, so 5 feet.
The area of half the circle is (3.14 x 5^2) / 2 = 39.25 square feet.
The area of the rectangle is 20 x 10 = 200 square feet.
Total area = 200 + 39.25 = 239.25 square feet.