Use these three reactions

CH4(g) + 2 O2(g) −→ CO2(g) + 2 H2O(g) ∆H◦ = −802 kJ
CH4(g) + CO2(g) −→ 2 CO(g) + 2 H2(g) ∆H◦ = 247 kJ
CH4(g) + H2O(g) −→ CO(g) + 3 H2(g) ∆H◦ = 206 kJ

to determine the appropriate enthalpy change of

CH4(g) + 3/2 O2(g) −→ CO(g) + 2 H2O(g).