Answer
$\frac{3}{x - 3}$, $x\ne3$
Work Step by Step
We must factor the top and bottom separately. First, we factor the top by pulling out a 3. Next, we factor the bottom as $(x - 3)(x - 3)$. The following results:
$\frac{3(x-3)}{(x-3)(x-3)}$
Then, we are allowed to cancel out the $x - 3$ factors.
This leads us to an answer of $\frac{3}{x - 3}$. Note that, since x = 3 is still a domain restriction (since it makes the denominator 0), we still must declare that $x\ne3$.