Answer
$2 \sqrt 3$
Work Step by Step
Let $A=(0,0,0)$ and $B=(2,-2,-2)$ be the two given points.
The distance between two points can be calculated as: $|AB|=\sqrt{(x-x_0)^2+(y-y_0)^2+(z-z_0)^2}$
Thus, we have
$|AB|=\sqrt{(2-0)^2+(-2-0)^2+(-2-0)^2}=\sqrt {4+4+4}=\sqrt{12}=2 \sqrt 3$
