1. **State the problem:** Express $\log_9(xy)$ in terms of $\log_3 x$ and $\log_3 y$. 2. **Recall the change of base formula:** For any positive numbers $a,b,c$ with $a \neq 1$, $$\log_a b = \frac{\log_c b}{\log_c a}$$ 3. **Apply the change of base formula to $\log_9(xy)$ using base 3:** $$\log_9(xy) = \frac{\log_3(xy)}{\log_3 9}$$ 4. **Simplify $\log_3 9$:** Since $9 = 3^2$, $$\log_3 9 = \log_3 3^2 = 2$$ 5. **Use the logarithm product rule:** $$\log_3(xy) = \log_3 x + \log_3 y$$ 6. **Substitute back into the expression:** $$\log_9(xy) = \frac{\log_3 x + \log_3 y}{2}$$ 7. **Final answer:** $$\boxed{\log_9(xy) = \frac{\log_3 x + \log_3 y}{2}}$$ This expresses $\log_9(xy)$ in terms of $\log_3 x$ and $\log_3 y$ clearly and simply.