Answer :
[tex]-ax+4b>9\ \ \ |Subtract\ 4b\ from\ each\ side\\\\
-ax>9-4b\ \ \ |Divide\ by\ -a\ from\ each\ side\\\\
x>\frac{9-4b}{-a}[/tex]
[tex]-ax+4b>9 \\\\ -ax>9-4b \\\\\boxed{ x> \frac{4b-9}{a}}[/tex]