Решите 6, 7 плз. Сори за качество

Решите задачу:

$6)(5m - 1)(m + 1) - 5m(m + 2)$
${5m}^{2} + 5m - m - 1 - {5m}^{2} - 10m \\ = - 6m - 1$
$- 6 \times ( - 1 \frac{5}{6} ) - 1 = - 6 \times ( - \frac{11}{6} ) \\ - 1 = 11 - 1 = 10$
$7)(2x - 5y)( - 4x - 3y) - \\ (x + 2y)( - 5x + 6y) =$
$- 8x {}^{2} - 6xy + 20xy + 15 {y}^{2} \\ - ( { - 5x}^{2} + 6xy - 10xy + {12y}^{2} ) =$
${ - 8x}^{2} + 14xy + {15y}^{2} + {5x}^{2} \\ + 4xy - 12 {y}^{2} = - 3 {x}^{2} + 18xy \\ + {3y}^{2}$