7x^3y^2÷[(-7)x^5y^3÷(1/3)x^3y^2]
=7x^3y^2÷(-7)x^5y^3×(1/3)x^3y^2
=7x^3y^2×(1/3)x^3y^2/(-7)x^5y^3
=-(1/3)xy