The Question: Polystyrene can be prepared by heating styrene with tribromobenzoyl peroxide in the absence of air. A sample prepared by this method has the empirical formula Br_{3}C_{6}H_{3}(C_{8}H_{8})_{n}, where the value of *n* can vary from sample to sample. If one sample has 10.46% Br, what is the value of *n*.

I know the answer is 19 but I have no clue how they got that. The "C_{6}H_{3}" part confuses me. I don't know how to find _{n} with something like that.

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I have no teacher right now so I really appreciate your help. Only two more chapters to go.