[latex]f(x)=x+5;\ D_f:x\in\mathbb{R}\\\\g(x)=2x+2;\ D_g:x\in\mathbb{R}\\\\D_f=D_g\ then:\\\\(f*g)(x)=f(x)*g(x)=g(x)*f(x)=(g*f)(x)\\\\conclusion:A=B\\\\AB.\\(f*g)(x)=(g*f)(x)=f(x)*g(x)=(x+5)(2x+2)\\\\=2x^2+2x+10x+10=2x^2+12x+10\\\\C.\\(f*g)(-2)=f(-2)*g(-2)=[(-2)+5]*[2(-2)+2]=(3)*(-4+2)\\\\=3(-2)=-6[/latex]

Open up the attachment below...