Hess's Law?

Question

The enthalpy of combustion of solid carbon to form carbon dioxide is -393.7 kJ/mol carbon, and the enthalpy of combustion of carbon monoxide to form carbon dioxide is -283.3 kJ/mol CO. Use these date to calculate delta H for the reaction

2C + O2 ----------> 2CO

Answer 1

2 x the first value minus 2 x the second value. Simple!