Find the distance of the point $\mathrm{P}(6,-6)$ from the origin.

Find the distance between the points $P\left(x_1,y_1\right)$ and $Q\left(x_2,y_2\right),$ when $PQ$ is parallel to the $x$-axis.

Find the distance between the points $\mathrm{P}\left(x_1,y_1\right)$ and $\mathrm{Q}\left(x_2,y_2\right),$ when $\mathrm{PQ}$ is parallel to the $y$-axis.