`A = (3x-2)(2x+10) - (2x+2)(3x+10)`

`= 6x^2 + 30x - 4x - 20 - ( 6x^2 + 20x + 6x + 20 )`

`= 6x^2 + 30x - 4x - 20 - 6x^2 - 20x - 6x - 20`

`= ( 6x^2 - 6x^2 ) + ( 30x - 4x - 20x - 6x ) - ( 20 + 20 )`

`= -40`

`B = (x-5)(2x+7) - 2x(x-5) - 7x + 2`

`= 2x^2 + 7x - 10x - 35 - 2x^2 + 10x - 7x + 2`

`= ( 2x^2 - 2x^2 ) + ( 7x - 10x + 10x - 7x ) - ( 35 - 2 )`

`= -33`

`C = 2(x-2)(x+3) - x(5x-4) + 3x(x-2) + 7`

`= (2x-4)(x+3) - 5x^2 + 4x + 3x^2 - 6x + 7`

`= 2x^2 + 6x - 4x - 12 - 5x^2 + 4x + 3x^2 - 6x + 7`

`= ( 2x^2  - 5x^2 + 3x^2 ) + ( 6x - 4x + 4x - 6x ) - ( 12 - 7 )`

`= -5`

`D = x(3x-1) - x^2(x+3) + (x-1)(x^2+x+2)`

`= 3x^2 - x - x^3 - 3x^2 + x^3 + x^2 + 2x - x^2 - x - 2`

`= ( 3x^2 - 3x^2 + x^2 - x^2 ) - ( x - 2x + x ) - ( x^3 - x^3 ) - 2`

`= -2`