If s is the length of an edge, then

the surface area of the cube = 6s² square centimeters, and

the volume of the cube = s³ cubic centimeters.

The number of cubic centimeters in the volume of the cube is equal to twice
the number of square centimeters in its surface area, so:

             s³ = 2∙6s²
             s³ = 12s²
      s³ - 12s² = 0
     s²(s - 12) = 0

s² = 0;  s - 12 = 0
 s = 0        s = 12

We ignore the humorous answer, s = 0 (which says that a cube reduced to a
point has 0 volume and 0 surface area, and 0 is indeed twice 0, lol).

Now seriously, a cube that has each edge measuring 12 centimeters has 
12³ = 1728 cubic centimeters of volume and 6∙12² = 864 square centimeters of
surface area.  Sure enough, 1728 is twice 864.

Answer: 1728

Edwin