Fe2O3+CO gives 2Fe+CO2
BALANCE THE EQUATION
You have oxygen coming from two reactants but it is only in one product. So focus on the CO + CO2. You have 3 oxygens in the iron oxide and one in the CO, but 2 in CO2 so you need a combination of oxygen in both reactants that results in an even number.
Fe2O3 + 3 CO --> 2 Fe + 3CO2