Question

Need help on where to begin please..

Determine the value of the equilibrium constant, Kgoal, for the reaction
CO2(g)→C(s)+O2(g), Kgoal=?
by making use of the following information:
2CO2(g)+2H2O(l)→CH3COOH(l)+2O2(g), K1=5.40×10−16
2H2(g)+O2(g)→2H2O(l), K2=1.06×1010
CH3COOH(l)→2C(s)+2H2(g)+O2(g), K3=2.68×10−9