To evaluate \( \frac{10^{-8}}{10^{-9}} \), we can use the property of exponents that states:
\[ \frac{a^m}{a^n} = a^{m-n} \]
Applying this rule here gives:
\[ \frac{10^{-8}}{10^{-9}} = 10^{-8 - (-9)} = 10^{-8 + 9} = 10^{1} \]
Thus,
\[ 10^{-8}/10^{-9} = 10^{1} = 10. \]
The final answer is:
\[ \boxed{10}. \]