Would it be easier if you looked at it like this:
[tex] \frac{10}{2} * \frac{ x^{2} }{x} * \frac{ y^{5} }{ y^{8} } [/tex]
In division exponents subtract:
[tex] \frac{10}{2} * \frac{ x^{2} }{x} * \frac{ y^{5} }{ y^{8} } = 5 * x * \frac{1}{ y^{3} } [/tex]
[tex]5 * x * \frac{1}{ y^{3} } = \frac{5x}{ y^{3} } [/tex]
