Помогите пожалуйста дам 18б.

3) -2(4y - 2x) + (y^2 - 3x) - y(y - x + 7) = -8y + 4x + y^2 - 3x - y^2 + xy - 7y = -8y + 4x - 3x + xy - 7y = xy - 15y + x

6)
$\frac{2x + 1}{6} = \frac{7x - 3}{12} + 1 \\ \frac{2(2x + 1)}{12} = \frac{7x - 3}{12} + \frac{12}{12} \\ \frac{4x + 2}{12} = \frac{7x + 9}{12} \\ 4x + 2 = 7x + 9 \\ 7x - 4x = 2 - 9 \\ 3x = - 7 \\ x = - \frac{7}{3} = - 2\frac{1}{3}$