1. **State the problem:** Find the domain of the function $$f(x) = \frac{x - 9}{x + 3}$$. 2. **Recall the domain rule for rational functions:** The domain includes all real numbers except where the denominator is zero because division by zero is undefined. 3. **Set the denominator equal to zero and solve:** $$x + 3 = 0$$ $$x = -3$$ 4. **Exclude this value from the domain:** The function is undefined at $$x = -3$$. 5. **Write the domain:** All real numbers except $$x = -3$$. 6. **Express the domain in interval notation:** $$(-\infty, -3) \cup (-3, \infty)$$. **Answer:** The correct choice is A: all real numbers except $$x = -3$$.