TeX source:
\begin{array}{ccl} \dfrac{4y \sqrt{x^3}}{16xy^2} &=& \dfrac{4x^{\frac{3}{2}}y}{16xy^2} \cr\cr &=& \dfrac{1}{4} x^{\frac{3}{2}-1}y^{1-2} \cr\cr &=& \dfrac{1}{4} x^{\frac{1}{2}}y^{-1} \cr\cr &=& \dfrac{\sqrt{x}}{4y} \end{array}