Basic arithmetic for finding distance between spheres :

Sqrt[(1-0)^2+(-1 - 1)^2+(0-1)^2] // N

Multiplication is "*"

2  * 3

4/6 // N

Plot implicit surfaces with "ContourPlot3D"

ContourPlot3D[ x^2+y^2+z^2==9, {x,-4,4}, {y,-4,4}, {z,-4,4} ]

ContourPlot3D[ x^2+y^2+z^2 == 9, {x,-4,4}, {y,-4,4}, {z,-4,4} ]

Plotting a plane as an implicit equation:

ContourPlot3D[ z  == 1, {x,-3,3}, {y,-3,3}, {z,-3,3}  ]

ContourPlot3D[  {(x-1)^2+(y+1)^2+z^2==9, x^2+(y-1)^2+(z-1)^2==16},  {x,-5,5}, {y,-5,6}, {z,-4,6}  ]