Question

Charge q/2 placed inside sphere, q on sphere and 2q at x distance of sphere

Answer 1

If it is a solid conducting sphere:

In the static condition, there is no electric field and no net charge at any point inside a conductor. The charge must appear at the surface of the conductor. Potential V at the centre or any point inside it is same and its value is that at its surface (a conductor is an equipotential volume). Hence

V=14πϵoqR