The given expression is:

$9 \log_9 (11)$

We can simplify this expression using the power rule of logarithms. The power rule states:

$a \log_a (x) = x$

In this case, $a = 9$, so applying the rule:

$9 \log_9 (11) = 11$

Thus, the simplified expression is:

$11$

Would you like more details or have any questions? Here are five related questions you might want to explore:

1. How do you simplify $5 \log_5 (25)$?
2. What is the value of $2 \log_2 (8)$?
3. How do logarithms with different bases affect simplification?
4. Can the expression $\log_b (b^x)$ be simplified further?
5. How would you solve $3 \log_3 (27)$?

Tip: When the base of a logarithm matches the coefficient, the expression simplifies directly to the argument inside the logarithm.