Răspuns :
[tex]Notam\ x=suma\ initiala\\
\frac{x}{4}+\frac{3}{5}(x-\frac{x}{4})+12,3=x\\
\\
\frac{x}{4}+\frac{3}{5}\cdot \frac{3x}{4}+12,3=x\\
\\
\frac{x}{4}+\frac{9x}{20}+12,3=x|\cdot 20\\
5x+9x+246=20x\\
14x+246=20x\\
6x=246\Rightarrow \bold{x=41\ lei}[/tex]