Question

Given the reactions, X(s)+1/2 O2(g)⟶XO(s) ΔH=−605.3 kJ XCO3(s)⟶XO(s)+CO2(g) ΔH=+380.3 kJ what is ΔH for this reaction? (in kilojoules) X(s)+1/2 O2(g)+CO2(g)⟶XCO3(s)