I have a complete explanation on this topic on my website. To find my website click on my tutor name "rapaljer" anywhere in algebra.com. There you will find a link to take you to my website. On the Homepage of my website, look for the link near the top of the page "Basic, Intermediate, and College Algebra: One Step at a Time." Next, click on "Basic Algebra", then look in Chapter 1, and click on Section 1.11 Inequalities.
Dr. Robert J. Rapalje, Retired
Seminole State College of Florida