The limit as x-approaches 3 of f(x) is x-3 over x squared -9

notice that the denominator can be factored into (x-3)(x+3).
Now you can cross out (x - 3) from the numerator and denomiantor resulting in a simplified fraction of [tex] \frac{1}{x+3} [/tex]
Plug the limit value (which is 3) into the simplified fraction.
Answer: [tex] \frac{1}{6} [/tex]