Thank you for the opportunity to help you with your question!

Here as the equation is unbalanced, so first balance th egiven equation.

4Fe + 3 O2 -> 2 Fe2O3

Now the mole ratio:

4 Fe/3 O2 = 1.33333.

Compare the actual value of the moles to the value you just got. So,

6.8 mol Fe/8.9 mol O2 = .7640.

It can be clearly observed that 7640 is less than 1.333, meaning that Fe is the limiting reagent. If the compared value of the moles were bigger than 1.333, then O2 would be limiting.

So Fe is your answer.

Please let me know if you need any clarification. I'm always happy to answer your questions.