#### Answer

$\frac{y^{2}}{2x}$

#### Work Step by Step

$\frac{5x^{2}}{y}\div\frac{10x^{3}}{y^{3}}$
$=\frac{5x^{2}}{y}\times\frac{y^{3}}{10x^{3}}$
$=\frac{x^{2}}{y}\times\frac{y^{3}}{2x^{3}}$
$=\frac{x\times x}{y}\times\frac{y\times y\times y}{2\times x\times x\times x}$
$=\frac{1}{1}\times\frac{y\times y}{2\times x}$
$=\frac{y^{2}}{2x}$