\[\boxed{\mathbf{720\ (720).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[5x^{2} + 4x - 13 = 0\]
\[3x_{1} \cdot x_{2} - x_{1} - x_{2} =\]
\[= 3x_{1} \cdot x_{2} - \left( x_{1} + x_{2} \right) =\]
\[= - \frac{3 \cdot 13}{5} + \frac{4}{5} = - \frac{39}{5} + \frac{4}{5} =\]
\[= - \frac{35}{5} = - 7.\]