Answer :
[tex]x-\ number\\\\
\frac{x-9}{2}=4\ \ \ |Multiply\ by\ 2\\\\
x-9=8\ \ \ |Add\ 9\\\\
x=17\\\\Number\ is\ 17.[/tex]
[tex](x-9):2=4 \\\\ x-9=4*2 \\\\ x-9=8 \\\\ x=8+9 \\\\ \boxed{x=17}[/tex]