E)\;\left(\frac{x^2+1}{2x-1}-\frac x2\right)\cdot\frac{1-2x}{x+2}=\left(-\frac{x^2+1}{1-2x}-\frac x2\right)\cdot\frac{1-2x}{x+2}=-\frac{x^2+1}{x+2}-\frac{x-2x^2}{2(x+2)}=\\=\frac{-2x^2-2-x+2x^2}{2(x+2)}=\frac{-x-2}{2(x+2)}=-\frac{x+2}{2(x+2)}=-\frac12\\\\3)\;\frac3{5x}-\frac3{x+y}\cdot\left(\frac{x+y}{5x}-x-y\right)=\frac3{5x}-\frac3{x+y}\cdot\left(\frac{x+y}{5x}-(x+y)\right)=\\=\frac3{5x}-\frac3{5x}+3=3