Systems A, B, and C are classical gases (not necessarily ideal), each with the same number of molecules N ( or same number of moles n if you prefer), where N is constant. We can measure pressures and volumes Pa,Va ; Pb,Vb ; and Pc,Vc for each system. When A and B are in thermal equilibrium, our measurements show that their pressure and volumes satisfy: PbVb-(beta)Pb-(alpha)Vb+(alpha)(beta)-PaVa=0 When A and C are in thermal equilibrium, we find: PcVc-PaVa-((gamma)PaVa)/Pc=0 where (alpha),(beta), and (gamma) are constants. Find the equation relating Pb,Vb and Pc,Vc that is satisfied when system B and C are in thermal equilibrium. Would I just set the equation for AB = AC and move the B and C's to one said and A to the other?