Алгебра: Помогите решить 102,желательно с объяснением,заранее спасибо.

Решите задачу:

$1) \: \: 2.4(5x - 10) - 5(x + 1) - 3(1 - 3x) = 2.4 \times 5x - 2.4 \times 10 - 5x - 5 - 3 + 3 \times 3x = 12x - 24 - 5x - 5 - 3 + 9x = 16x - 32 = 16(x - 2)$
$2) \: \: - 2x(x + 4) + 5( {x}^{2} - 3x) = - 2x \times x - 2x \times 4 + 5 {x}^{2} - 5 \times 3x = - 2 {x}^{2} - 8x + 5 {x}^{2} - 15x = 3 {x}^{2} - 23x$
$3) \: \: 3a(3a - {a}^{2} ) - 4a(2 {a}^{2} - 5a) = 3a \times 3a - 3a \times {a}^{2} - 4a \times 2 {a}^{2} + 4a \times 5a = 9 {a}^{2} - 3 {a}^{3} - 8 {a}^{3} + 20 {a}^{2} = 29 {a}^{2} - 11 {a}^{3}$
$4) \: \: 3m(n - 2m) - m(m + 4n) = 3mn - 3m \times 2m - m \times m - m \times 4n = 3mn - 6 {m}^{2} - {m}^{2} - 4mn = - 7 {m}^{2} - mn$
$5) \: \: 0.3 {x}^{2} ( {x}^{2} - 3x + 2) - 0.6x(2 {x}^{3} + 6 {x}^{2} - 4x) = 0.3 {x}^{2} \times {x}^{2} - 0.3 {x}^{2} \times 3x + 0.3 {x}^{2} \times 2 - 0.6x \times 2 {x}^{3} - 0.6x \times 6 {x}^{2} + 0.6x \times 4x = 0.3 {x}^{4} - 0.9 {x}^{3} + 0.6 {x}^{2} - 1.2 {x}^{4} - 3.6 {x}^{3} + 2.4 {x}^{2} = - 0.9 {x}^{4} - 4.5 {x}^{3} + 3 {x}^{2}$
$6) \: \: 4x(7y - 3 {x}^{2} ) - 3y(x - {y}^{2} ) = 4x \times 7y - 4x \times 3 {x}^{2} - 3yx + 3y \times {y}^{2} = 28xy - 12 {x}^{3} - 3xy + 3 {y}^{3} = - 12 {x}^{3} + 25xy + 3 {y}^{3}$
$7) \: \: 5a(3 {a}^{2} - 2b) + 17b(2a + b) - 3a( - 4b + a) = 5a \times 3 {a}^{2} - 5a \times 2b + 17b \times 2a + 17 {b}^{2} + 3a \times 4b - 3 {a}^{2} = 15 {a}^{3} - 10ab + 34ab + 17 {b}^{2} + 12ab - 3 {a}^{2} = 15 {a}^{3} + 36ab + 17 {b}^{2} - 3 {a}^{2}$
$8) \: \: 2 {x}^{3} (3x - 1) - 4x( {x}^{3} - 2 {x}^{2} + 3x) - 5x - 2 {x}^{4} = 2 {x}^{3} \times 3x - 2 {x}^{3} - 4x \times {x}^{3} + 4x \times 2 {x}^{2} - 4x \times 3x - 5x - 2 {x}^{4} = 6 {x}^{4} - 2 {x}^{3} - 4 {x}^{4} + 8 {x}^{3} - 12 {x}^{2} - 5x - 2 {x}^{4} = 6 {x}^{3} - 12 {x}^{2} - 5x$