Combustion

Can anyone help?

Calculate the equilibrium composition for the reaction H2O to H2 + ½ O2 for the
ratios on n(H)/n(O) = 1.5. The temperature is 2500K, and the pressure is 3 atm.

I have done it for n(H)/n(O) = 2, which was much easier as H20 cancelled out however cannot do it with a ratio of 1.5.

Thanks