①(-0.2xy)(5x)= (-0.2*5)*(x*x)*y=-x²y
②（三分之四xy³）（-八分之三x²y）=(-4/3*3/8)*(x*x²)*(y³*y)=-1/2x³y^4
3)当x=( -4 )时,3x(2x-5)+2x(1-3x)=52

希望采纳!