Răspuns:
[tex]( \frac{2}{5} - \frac{2}{5} x) \div \frac{2}{5} = 0.16[/tex]
[tex] \frac{2}{5} \div \frac{2}{5} - \frac{2}{5} x \div \frac{2}{5} = \frac{16}{100} [/tex]
[tex]1 - x = \frac{4}{25} \: | \times 25[/tex]
[tex]25 - 25x = 4[/tex]
[tex] - 25x = 4 - 25[/tex]
[tex] - 25x = - 21 \: | \times ( - 1)[/tex]
[tex]25x = 21[/tex]
[tex]x = \frac{21}{25} \: \in \: \mathbb{Q}[/tex]
