P4 (g) + 3O2 (g) <-> P4O6(s)

At a particular temperature, Keq = 4.6. If [P4O6] at this temperature is 1.2M, calculate the concentration of P4 and O2

I'd rather have someone tell me how to do it, so I can do it myself since it's in preparation for an exam.

Don't the P4 and O2 concentrations at equilibrium depend upon their initial concentrations and/or the concn of P4O6 initially.