We should start by plotting these points on the coordinate plan and drawing the pool.
Looking at the diagram I've attached, we can split the pool into two rectangles and find the area of each.
For the smaller rectangle, with vertices
![(0,2), (0,5), (2,5), (2,2)](https://tex.z-dn.net/?f=%280%2C2%29%2C%20%280%2C5%29%2C%20%282%2C5%29%2C%20%282%2C2%29)
, the length is 3 units and the width is 2 units.
![A=lw=(2\ u)(3 \ u)=6 \ u^2](https://tex.z-dn.net/?f=A%3Dlw%3D%282%5C%20u%29%283%20%5C%20u%29%3D6%20%5C%20u%5E2)
For the larger rectangle with vertices
![(2,6),(5,6),(5,1),(2,1)](https://tex.z-dn.net/?f=%282%2C6%29%2C%285%2C6%29%2C%285%2C1%29%2C%282%2C1%29)
, the length is 5 units and the width is 3 units.
![A=lw=(5\ u)(3 \ u)=15 \ u^2](https://tex.z-dn.net/?f=A%3Dlw%3D%285%5C%20u%29%283%20%5C%20u%29%3D15%20%5C%20u%5E2)
![A_{total}=15 \ u^2+6 \ u^2 = 21 \ u^2](https://tex.z-dn.net/?f=A_%7Btotal%7D%3D15%20%5C%20u%5E2%2B6%20%5C%20u%5E2%20%3D%2021%20%5C%20u%5E2)
Now remember, each square unit on the coordinate plane represents 9 square feet, so we write: