Hi there,
Have you missed out a line of your equation or mistyped something because as far as I can see you can't get it from the information you have provided.
Also in regards to how to work it out. Its a bit like a jigsaw, if you look for your starting piece (or pieces) or reactants in your overall equation, in this case FeO (g) and CO (g) and your ending pieces or your products - Fe (s) and CO
2 and try and fit in the equations you have been given to get from start to finish. To do this you may have to reverse a reaction (for instance 3FeO (s) + CO
2 Fe
3O
4 + CO) However remember to reverse your enthalpy (:delta:H) values as well. So in this example it would be -18kJ. It is also okay to multiply your equations to fit as well providing you change your enthalpy numbers to support this