If your solving for x, you need to isolate/get the variable "x" by itself in the inequality:
-24 ≤ 3x - 9 First add 9 on both sides
-24 + 9 ≤ 3x - 9 + 9
-15 ≤ 3x Then divide 3 on both sides to get "x" by itself
-5 ≤ x [or x ≥ -5 if you prefer "x" to be on the left side]