The main issue here comes down to identifying what type of question this is. You state it explicitly yourself:
I have a "limiting reactants" textbook problem
Have you come across such problems before? If so, you should recognise that one of the reactants is in excess whilst the other is a limit - that is, it reacts completely with the excess reactant to give the product, leaving some of the excess reactant left over.
Can you identify which reactant is the limit?
Also, as a side note, make sure that you are using the molar mass of Br2
not Br in your second line of equations! The bromine that the textbook is talking about is Br2