#### Answer

$a.\quad x=3$
$b.\quad y=-1$
$c.\quad z=-2$

#### Work Step by Step

$a.\quad $
A plane perpendicular to the x-axis is the yz-plane, $x=0.$
A plane parallel to it, passing through the point (3,0,0), is $x=3$
$b.\quad $
A plane perpendicular to the y-axis is the xz-plane, $y=0.$
A plane parallel to it, passing through the point (0,$-1$,0), is $y=-1$
$c.\quad $
A plane perpendicular to the z-axis is the xy-plane, $z=0.$
A plane parallel to it, passing through the point ($0,0,-2$), is $z=-2$