Which expression is equivalent to the following complex fraction? \( \frac{\frac{x}{x-3}}{\frac{x^{2}}{x^{2}-9}} \)

\[ \textbf{Step 1: Write the complex fraction as a division.} \] \[ \frac{\frac{x}{x-3}}{\frac{x^2}{x^2-9}} = \frac{x}{x-3} \div \frac{x^2}{x^2-9} \] \[ \textbf{Step 2: Replace the division with multiplication by the reciprocal.} \] \[ \frac{x}{x-3} \times \frac{x^2-9}{x^2} \] \[ \textbf{Step 3: Factor the expression in the numerator where appropriate.} \] Notice that: \[ x^2-9 = (x-3)(x+3) \] Thus, the expression becomes: \[ \frac{x}{x-3} \times \frac{(x-3)(x+3)}{x^2} \] \[ \textbf{Step 4: Cancel the common factor \((x-3)\).} \] \[ \frac{x}{\cancel{x-3}} \times \frac{\cancel{x-3}(x+3)}{x^2} = \frac{x(x+3)}{x^2} \] \[ \textbf{Step 5: Simplify by cancelling a factor of \(x\) from the numerator and denominator.} \] \[ \frac{x(x+3)}{x^2} = \frac{x+3}{x} \quad \text{(assuming \(x \neq 0\))} \] \[ \textbf{Final Answer:} \] \[ \frac{x+3}{x} \]