[tex] 8^{-10} [/tex] can be converted into [tex] \frac{1}{ 8^{10} } [/tex] , and applying this to [tex] 8^{-5} [/tex] can see that
[tex] \frac{ \frac{1}{ 8^{10} } }{ \frac{1}{ 8^{5} } } [/tex]
This gives us
[tex] \frac{ 8^{5} }{ 8^{10} } = \frac{1}{ 8^{5} } = 8^{-5} [/tex]
