To simplify the expression \( 13^{-5} \cdot 13^{-11} \) using the properties of exponents, you can apply the property that states \( a^m \cdot a^n = a^{m+n} \).
So, we have:
\[ 13^{-5} \cdot 13^{-11} = 13^{-5 + (-11)} = 13^{-16} \]
Now, to convert this to an expression with only positive exponents, we use the property that \( a^{-n} = \frac{1}{a^n} \):
\[ 13^{-16} = \frac{1}{13^{16}} \]
Now, looking at the answer choices you provided:
- \( \frac{1}{26^6} \)
- \( \frac{1}{13^6} \)
- \( \frac{1}{13^{16}} \)
- \( \frac{1}{26^{16}} \)
The equivalent expression to \( 13^{-5} \cdot 13^{-11} \) with only positive exponents is:
\[ \frac{1}{13^{16}} \]
So, the correct answer is \( \frac{1}{13^{16}} \).