$Fe_2O_3 + 3CO ⟶ 2Fe + 3CO_2$ is a redox reaction, but not a combination reaction.Redox reactions are oxidation and reduction reactions.It is a chemical reaction in which the oxidation states of the reactants are changed.The oxidation and reduction reactions always occurs simultaneously.In oxidation, loss of electrons takes places.In reduction, gain of electrons takes place.Combination reaction is a type of reaction in which two reactants combines to form a product.The above reaction is not a combination reaction but it is a redox reaction as oxidation and reduction is taking place simultaneously in this reaction. Carbon monoxide (CO) acts as a reducing agent and fe as an oxidising agent.