How far apart are the points $(2,0,0)$ and $(-3,0,0)$?

Show that the points $P(-2, 3, 5)$,$Q(1, 2, 3)$,and $R(7, 0, -1)$ are collinear.

Find the distance between the following pairs of points: $(2, -1, 3)$ and $(-2, 1, 3)$.

If the sum of the squares of the distances of a point from the three coordinate axes is $36$,then its distance from the origin is:

Fill in the blanks:
The $x$-axis and $y$-axis taken together determine a plane known as........

Let $A, B, C$ be the feet of the perpendiculars from a point $P$ on the $xy, yz,$ and $zx$-planes respectively. Find the coordinates of $A, B, C$ for the following points $P$:
$(3, 4, 5), (-5, 3, 7), (4, -3, -5)$