[tex]5s-9 < 2s+12\ \ \ \ \ |\text{add 9 to both sides}\\\\5s < 2s+21\ \ \ \ |\text{subtract 2s from both sides}\\\\3s < 21\ \ \ \ |\text{divide both sides by 3}\\\\\boxed{x < 7\to s\in(-\infty,\ 7)}[/tex]
