Answer :
[tex]\frac{(10ac-x)}{11}=-3 \\\\ 10ac-x=-33 \\\\ 10ac=-33+x \\\\ \boxed{a=\frac{x-33}{10c}}[/tex]
[tex]\frac{(10ac-x)}{11}=-3\ \ \ \ | multiply\ by\ 11\\\\
10ac-x=-33\ \ \ \ | add\ x\\\\
10ac=-33+x\ \ \ \ | divide\ by\ 10c\\\\
\boxed{a=\frac{-33+x}{10c}}[/tex]