For the complete answer to the question above, phi = q/(6*epsilon(0))
Gauss' law tells us that the total flux through a closed surface, in this case, a cube, is equal to the charge enclosed, q, divided by epsilon(0).
phi = q/epsilon(0)
Since the point charge is in the center of the cube, each face will have an equal amount of flux going through it, i.e. one-sixth.
This gives us
phi = q/(6*epsilon(0))
