Mr. hann is trying to decide how many new copies of a book to order for his students. each book weighs 6 ounces. which ordered pair is a viable solution if x represents the number of books he orders and y represents the total weight of the books, in ounces? (–3, –18) (–0.5, –3) (0, 0) (0.5, 3)

Only 0,0    You don't order negative numbers of books which eliminates the first two pairs.  And you don't order 1/2 a book which eliminates the last pair.

If you order 0 shirts they will weight 0 ounces is the only viable solution.
Yet I consider this a trick question since you don't fill out an order form for 0 books.  Perhaps the answer is none of them??

The mode of the numbers is 29.