\[\left\{ \begin{matrix}
- 0,4x < 2,5\ \ \ \ \\
- 0,5x \geq 3,1\ \ \ \ \\
1,05x \geq - 6,51 \\
\end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix}
x > - \frac{25}{4}\text{\ \ } \\
x \leq - \frac{31}{5}\text{\ \ } \\
x \geq - \frac{651}{105} \\
\end{matrix} \right.\ \]
\[\left\{ \begin{matrix}
x > - 6,25 \\
x \leq - 6,2\ \ \\
x \geq - 6,2\ \ \ \\
\end{matrix} \right.\ \Longrightarrow x = - 6,2.\]
\[Ответ:\ - 6,2.\]