so 3 times a number is between -18 and 18
between means it cannot be -18 or 18 so
3 times x=3x
x=unknown
3x
< less than
>greater than
if it is between -18 and 18 then the number is >-18 and <18 so
-18<3x and
18>3x
divide both equations by 3
-6<x
6>x
combine
-6<x<6
solution set=(x|-6<x<6)
