Ответ:
\[\frac{13}{25} - \left( x + \frac{6}{25} \right) = \frac{4}{25}\]
\[x + \frac{6}{25} = \frac{13}{25} - \frac{4}{25}\]
\[x + \frac{6}{25} = \frac{9}{25}\]
\[x = \frac{9}{25} - \frac{6}{25}\]
\[x = \frac{3}{25}.\]
\[\frac{13}{25} - \left( x + \frac{6}{25} \right) = \frac{4}{25}\]
\[x + \frac{6}{25} = \frac{13}{25} - \frac{4}{25}\]
\[x + \frac{6}{25} = \frac{9}{25}\]
\[x = \frac{9}{25} - \frac{6}{25}\]
\[x = \frac{3}{25}.\]