The inequality is .

Apply addition property of inequality: Add 13.5 to each side.

      (Comutative property: )

                     (Additive inverse property: )

                           (Additive identity property: )

                         (Divide: )

                                     (Add: )

Graph the solution set on a number line

Note: A circle means that this point is not included in the solution set.

Check:

To check, substitute a number less than 3.9, in .

   (Substitute )

             (Subtract: )

The inequality is true.

The inequality solution set is .