The area of a rectangular or square shape can be found by using the following formula:

We were told that the length is nine times the width, therefore:

If we replace the expression for the length above on the expression for the area, we will obtain the following formula:

We can replace A with the value of the area to solve for the width:
![\begin{gathered} 81=9\cdot\text{width}^2 \\ \text{width}^2=(81)/(9) \\ \text{width}^2=9 \\ \text{width}=\sqrt[]{9} \\ \text{width}=3\text{ yards} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/hvhpgvisgmuech1n5rzexb75pce5vruaud.png)
The width of the garden is 3 yards.