Answer
$$9\sqrt{3}$$
Work Step by Step
We are given the following equation:
$$ A\left(s\right)=\frac{\sqrt{3}}{4}s^2$$
Thus, when the side length is 6, it follows:
$$ \frac{\sqrt{3}}{4}\left(6^2\right)\\ \frac{\sqrt{3}\cdot \:6^2}{4}\\ 9\sqrt{3}$$