[tex]A=3x^2- xy,\ \ B=-2y,\ \ C=3x\\\\a)\\\\ (A*B)*C =((3x^2-xy)*(-2y))*3x=(-6x^2y+2xy^2)*3x=-18x^3y+6x^2y^2[/tex]
[tex]b)\\\\ A*(B *C) = (3x^2-xy)*((-2y) *3x)=(3x^2-xy)* (-6xy) =-18x^3y+6x^2y^2[/tex]
[tex]c)\\\\ ( A+B)*C = (3x^2-xy +(-2y)) *3x =(3x^2-xy -2y) *3x =9x^3-3x^2y+6xy[/tex]
[tex]c)\\\\ A*C+B *C = (3x^2-xy )*3x+(-2y) *3x = 9x^3-3x^2y-6xy[/tex]
