Consider the question. At the bookstore, Sarah bought 6 paperback books and 4 hardback books. Her brother bought one-third as many paperback books as Sarah bought, and two times the number of hardback books that she bought. How many books did her brother buy in total?
 If the answer is '10'; explain the reasoning:
Her brother bought 6 / 3 = 2 paperbacks. He bought 4 * 2 = 8 hardbacks. In total he bought 2 + 8 = 10 books.