Evaluating Rational Expressions

Samantha is working with a rational expression given by the function:

$$ f(x) = \f\frac{2x^2 - 8}{x^2 - 4} $$

She needs to simplify this expression. What is the value of the rational expression when evaluated at $x = 3$? Write your answer in simplest form as a fraction. Do not include spaces between the numerator and the denominator.