\[5x(x - 4) - x(3 + 5x) = 4\]
\[5x^{2} - 20x - 3x - 5x^{2} = 4\]
\[- 23x = 4\]
\[x = - \frac{4}{23}\]
\[Ответ:\ x = - \frac{4}{23}.\]