[tex]\sf ^{100)}x- \frac{20x}{100}= \frac{80x}{100}= \frac{4x}{5} \\ \\
\frac{4x}{5}- \frac{^2\not 10}{^{25}\not 100}* \frac{\not 4x}{\not 5}= \frac{2x}{25} \\ \\
^{5)}\frac{4x}{5}- \frac{2x}{25}=1872 \\ \\
\frac{20x}{25}- \frac{2x}{25}=1872 \\ \\
\frac{18x}{25}=1872 \\ \\
18x=46800 \\ \\
\boxed{\sf x=2600~lei} [/tex]