Answer:
[tex]\large\boxed{a.\ y=24}[/tex]
Step-by-step explanation:
[tex]\dfrac{y-9}{5}=3\qquad\text{multiply both sides by 5}\\\\5\!\!\!\!\diagup^1\cdot\dfrac{y-9}{5\!\!\!\!\diagup_1}=5\cdot3\\\\y-9=15\qquad\text{add 9 to both sides}\\\\y-9+9=15+9\\\\y=24[/tex]