Answer :
[tex]9x-\ nursers\\
y-\ doctors\\\\
\left \{ {{y=2x} \atop {9x+y=77}} \right. \\
sustitution\ method\\\\
9x+2x=77\\
11x=77\ \ \ | divide\ by\ 11\\
x=7\\\\
9x=9*7=63\\
2x=2*7=14\\\\
There\ are\ 63\ nursers\ and \ 14\ doctors.[/tex]