Answer:
12 m by 12 m
Step-by-step explanation:
You want the dimensions of a square pool with a 3 m deck all around if the total area of pool and deck is 324 m².
Deck
The 3 m width of the deck adds 2×3 m = 6 m to the overall length and width of the installation.
Dimensions
If the area of the square installation is 324 m², then the length of each side of it will be ...
√(324 m²) = 18 m
The side of the pool will be ...
18 m -6 m = 12 m
The pool is 12 meters square.
