The inequality is .

(Apply subtraction property of inequality:

For any real number, a, b, and c: If a < b then )

       (Subtract 18 from each side)

(Apply division property of inequality:

For any real number, 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 circle means that this point is not included in the solution set.

The solution set of the inequality is .