Explain why graphing the solutions of an inequality is more efficient than listing all the solutions of the inequality.

The saying "A picture is worth a thousand words" comes to mind here. You can list all of the possible points in a solution region, or you can list a few points to give the general pattern. Though this method requires a bit more work than simply graphing and showing the solution shaded region. A visual is often more efficient at conveying a message especially to those who aren't proficient with algebra. I'm sure there are other reasons why graphs are the better choice, but that's all I could think of really.