Explanation:
You gotta split it in two: in a rectangular and semicircle(which you can imagine as a full circle).
The area of the rectangular is easy that's just the width×the hight which is -> 32×20=640 ft^2
The area of the circle is easily found too we just have to use a little imagination.
The area of a FULL circle = pi × r^2
We know the diameter of the circle which=20 ft because the height of the rectangular is the same on both sides and the other side is the diameter of the circle so it's 20 ft
But in the formal we need the radius not the diameter, so we just divide the 20 in 2. 20÷2=10ft r=10ft
now just fill in the formula: pi(3.14)×10^2=314,159265359
so now we know the area of a FULL circle, but the cicle in the picture is only half a circle so we simply divide the full circle. 314.159265359÷2=157.0796326795
Now we just add the areas of both shapes together and we got the area of the garden. So 640+157.0796326795=797.0796326795 ft^2
Hope it helps, tell me if anything is unclear