Answer:
4Fe + 3O2 ---> 2Fe2O3
Explanation:
To properly balance the oxygen atoms you have to double them and make them even on the product side, then afterwards you match the the now 6 oxygen's on the product side with the oxygen's on the reactant side by putting a 3 in front of O2 to get 6 oxygen molecules on the reactant side. Afterwards all you have to do is match up the Iron atoms, so you just put a 4 in front of the Iron on the reactant side and then it matches with the 4 Iron on the product side. We used to have two Iron of the product side but after putting two infront of the product compound it doubled our Iron on that side and thats why were putting 4 infront of the reactants Iron.