Упростите выражение и найдите его значение (номер 9. 1-3)Помогите пожалуйста

1.
$8 - 12m - 6 + m - 6m - 8 = \\ = - 17m - 6$
при m=-0.3
$- 17m - 6 = - 17 \times ( - 0.3) - 6 = \\ = 5.1 - 6 = - 0.9$

2.
$- 0.5 + 1.5n + 0.8n - 0.4 + 0.1 + 0.7n = \\ = 3n- 0.8$
при n=0.21
$3n - 0.8 = 3 \times 0.21 - 0.8 = \\ =0 .63 - 0.8 = - 0.17$
3.
$3xy - 6x + 15y + 4xy + 6x - 12y = \\ = 7xy + 3y$
при х=9/7, у=-5/6
$7xy + 3y = \\ = 7 \times \frac{9}{7} \times ( - \frac{5}{6} ) + 3 \times ( - \frac{5}{6 }) = \\ = 9 \times ( - \frac{5}{6} ) - \frac{5}{2} = \\ = - \frac{45}{6} - \frac{15}{6} = \\ = - \frac{60}{6} = - 10$