[tex]Raspuns:\\
ms=500g\\
C=9\%\\
------------\\
ma=?\\
------------\\
ms=ma+md\\
\boxed{ma=ms-md}\\
C= \frac{md}{ms} *100\\
\boxed{md= \frac{C*ms}{100} }\\\\
Inlocuim:\\
md= \frac{500*9}{100} \\\
md= \frac{4500}{100} \\
\boxed{md=45}\\
ma=500-45\\
\boxed{ma=455}.
[/tex]