Chapter 1 - 1.7 - Linear Inequalities in One Variable - 1.7 Exercises - Page 139: 110

False. It is true only if $c\geq0$

$a\leq b$ If $c$ is positive: $ac\leq bc$ If $c$ is negative, then $-c$ is positive: $a(-c)\leq b(-c)$ $-ac\leq -bc$ $ac\geq bc$ If $c=0$: $a(0)=b(0)$ See Property 4 on page 132.