Answer
$d\approx3.464
\text{ units}
$
Work Step by Step
Using $d=\sqrt{(x_1-x_2)^2+(y_1-y_2)^2}$ or the Distance Formula, the distance, $d$, between the given points, $\left(
-\sqrt{6},\sqrt{6}
\right) \text{ and } \left(
0,0
\right),$ is
\begin{array}{l}\require{cancel}
d=\sqrt{ \left(-\sqrt{6}-0 \right)^2+\left(\sqrt{6}-0 \right)^2}
\\\\
d=\sqrt{ \left( -\sqrt{6} \right)^2+\left( \sqrt{6} \right)^2}
\\\\
d=\sqrt{ 6+6}
\\\\
d=\sqrt{ 12}
\\\\
d\approx3.464
\text{ units}
.\end{array}