1)`7x(x-5)+3(x-2)=7x^2-35x+3x-6=7x^2+(-35x+3x)-6=7x^2-32x-6`
2)`4x^2-2x+3x(x-5)=4x^2-2x+3x^2-15x=(4x^2+3x^2)+(-2x-15x)=7x^2-17x`
3) `5x^2y(\frac{1}{2}xy^2- \frac{1}{5}xy^2)=5x^2y(\frac{1}{2}- \frac{1}{5})xy^2=5x^2y.\frac{3}{10} xy^2=\frac{3}{2}x^3y^3`