Bjr,
[tex]A=5x-3(x+12)\\
A = 5x-(3\times x+3\times 12)\\
A = 5x-3x-36\\
A = 2x-36\\\\
B =3x-6+7(2x+4)\\
B = 3x-6+(7\times 2x+7\times4)\\
B = 3x-6+14x+28\\
B = 17x+22\\\\
C = 2x^2+x(4x-5)\\
C = x^2 + (x\times4x+x\times(-5))\\
C = x^2+4x^2-5x\\ C = 5x^2-5x\\\\
D = 4x^2 - x + x(5x-9)\\
D = 4x^2 - x + (x\times5x+x\times(-9))\\
D = 4x^2-x+5x^2-9x\\
D = 9x^2-10x\\\\[/tex]