[tex](5x - 3)(x - 4) - 3x(2x - 5) = \\ 5x \times x - 5x \times 4 - 3 \times x + 3 \times 4 - (3x \times 2x - 3x \times ( - 5)) = \\ 5 {x}^{2} - 20x -3x - 12 - (6 {x}^{2} - 15x) = \\ 5 {x }^{2} - 20x - 3x - 12 - 6 {x}^{2} + 15x = \\ - {x}^{2} - 8x - 12[/tex]
