Oxidation Problem. 2Fe2O3 + 3C ---> 4 Fe + 3 CO2?

I don't understand why Carbon has a +4 Charge and why Fe2 has a +3 charge. Does it Criss Cross with O3 to do that? I thought the problem was supposed to balance out to a 0 charge. Fe = +3 O= -2 charges. The elements alone are 0 charges I understand. Then the right side Carbon +4 and O= -2