Simple....
so you have...
[tex]- \frac{s}{3} \geq 6[/tex]
You want to isolate the variable, s, so multiply both sides of the equation by 3 to get rid of the fraction...
[tex]3*- \frac{s}{3} \geq 6*3[/tex]
Leaving you with...
-s[tex] \geq 18[/tex]
Now you can divide...but remember when you divide by a negative for any equality the sign flips....
Making your answer....
[tex]s \leq -18[/tex]
Thus, your answer.