$A=x(x-3xy)-(4y-5x^2).\dfrac{3}{5}y$
$=x^2-3x^2y-\dfrac{12}{5}y^2+3x^2y$
$=x^2-\dfrac{12}{5}y^2$
$=(-2)^2-\dfrac{12}{5}.\bigg(\dfrac{-1}{2}\bigg)^2$
$=\dfrac{17}{5}$
$B=(y-3x)2x+(4y+\dfrac{2}{3}x)4x$
$=2xy-6x^2+16xy+\dfrac{8}{3}x^2$
$=18xy-\dfrac{10}{3}x^2$
$=18(-1)(\dfrac{1}{18})-\dfrac{10}{3}.(\dfrac{1}{18})^2$
$=\dfrac{-491}{486}$
$C=5x(4x^2-2x+1)-2x(10x^2-5x-2)$
$=20x^3-10x^2+5x-20x^3+10x^2+4x$
$=9x$
$=9.15=135$
$D=x(x^2+y)-x^2(x-y)-xy(x-1)$
$=x^3+xy-x^3+x^2y-x^2y+xy$
$=2xy$
$=2.(-\dfrac{1}{2}).3=-3$
$E=(y^2+2)(y-4)-(2y^2+1)(\dfrac{1}{2}y-2)$
$=y^3-4y^2+2y-8-y^3+4y^2+\dfrac{1}{2}y+2$
$=\dfrac{3}{2}y-6$
$=\dfrac{3}{2}.4-6$
$=0$
