Помогите с алгеброй 7 класч

Здравствуйте!

1)
$5 + x {}^{2} = (x + 11)(x - 6) - x \\ 5 + x {}^{2} = x {}^{2} + 4x - 66 \\ - 4x + 66 + 5 = 0 \\ - 4x + 71 = 0 \\ - 4x = - 71 \\ 4x = 71 \\ x = 17.75$
2)
$\frac{4x + 3}{4} - \frac{7x + 1}{8} = 2 \\ \\ 2(4x + 3) - (7x + 1) = 16 \\ 8x + 6 - 7x - 1 - 16 = 0 \\ x - 11 = 0 \\ x = 11$
3)
$(n - 4)(n + 39) - (n - 3)(n + 31) = \\ = n {}^{2} + 35n - 156 - n {}^{2} + 28n - 93 = \\ = 63n - 249$