\(-3x^2y:xy=-3\left(x^2y:xy\right)=-3x\)
\(2a^3b^3:\left(-2ab^2\right)=\left(2:-2\right)\left(a^3:a\right)\left(b^3:b^2\right)=-a^2b\)
\(\dfrac{1}{5}m^2n^3:\left(-5m^2n^2\right)=\left(\dfrac{1}{5}:-5\right)\left(m^2:m^2\right)\left(n^3:n^2\right)=-\dfrac{1}{25}n\)