\[\boxed{\mathbf{727\ (727).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[2x_{1} - 5x_{2} = 28\]
\[x^{2} - 7x + m = 0\]
\[2 \cdot \left( 7 - x_{2} \right) - 5x_{2} = 28\]
\[14 - 2x_{2} - 5x_{2} = 28\]
\[- 7x_{2} = 14\]
\[x_{2} = - 2\]
\[x_{1} = 7 + 2 = 9\]
\[x_{1}x_{2} = m\]
\[- 2 \cdot 9 = - 18\]
\[Ответ:\ x_{1} = 9;\ \ \ x_{2} = - 2;\ \ \ \]
\[m = - 18.\]