[tex] \dfrac{6}{10x^2}\div\dfrac{6}{10x^3+60x^2}=\dfrac{6}{10x^2}\cdot\dfrac{10x^3-60x^2}{6}\\\\=\dfrac{1}{10x^2}\cdot\dfrac{10x^2(x-6)}{1}=x-6\to A. [/tex]
