[tex]17. \text{Se noteaza cu x suma initiala.}\\
x-\dfrac{2}{5}\cdot x-19=8|\cdot 5\\
5x-2x-95=40\\
3x=135\\
\boxed{x=45\ lei}\\ \text{In prima zi a cheltuit:} \dfrac{2}{5}\cdot 45=\boxed{18\ lei}\\
\\
18.\text{Se noteaza cu x pretul initial.}\\
x-\dfrac{5}{100}\cdot x-\dfrac{5}{100}\left(x-\dfrac{5}{100}\cdot x\right)=3610\\
x-\dfrac{x}{20}-\dfrac{1}{20}\left( x-\dfrac{x}{20}\right)=3610\\
\dfrac{19x}{20}-\dfrac{19x}{400}=3610|\cdot 400\\
\\
380x-19x=1444000\\
361x=1444000\Rightarrow \boxed{x=4000\ lei}[/tex]
