To solve for "x", you need to isolate/get the variable "x" by itself in the inequality:
9 + 6x < -15 First subtract 9 on both sides
9 - 9 + 6x < -15 - 9
6x < -24 Divide 6 on both sides to get "x" by itself
[tex]\frac{6x}{6} <\frac{-24}{6}[/tex]
x < -4