The area of an equilateral triangle can be found using the formula:
[tex]Area= \frac{ \sqrt{3} }{4}s^2 \ \ \ \ \ \text{[s= length of a side] } \\ \\ \\ \frac{ \sqrt{3} }{4}s^2=9 \sqrt{3} \\ \\ s^2=9 \sqrt{3}: \frac{ \sqrt{3} }{4}= 9 \sqrt{3} \cdot \frac{ 4 }{ \sqrt{3} }=36 \\ \\ s= \sqrt{36}=6 \ \text{ft } [/tex]
The answer is 6 ft.