The inequality is .

(Apply division property of inequality:

For any real numbers, a, b, and c: if a b then )

      (Divide each side by 3)

    (Multiply each side by negative one and flip the symbol)

               (Product of two same signs is positive)

The graph of the solution set on a number line diagram.

Note: A dot means that this point is included in the solution set.

The solution set of the inequality is .