This question is very similar to Example #3 in this section (§2.3). Note: You can NOT answer this question by direct substitution.

Evaluate this limit as demonstrated in this Example:
$\displaystyle \lim_{{{x}\rightarrow{4}}}\frac{{{x}^{{2}}-{7}{x}+{12}}}{{{x}-{4}}}=\lim_{{{x}\rightarrow{4}}}$ Preview Question 6 Part 1 of 2   (factor the numerator and cancel the common factor)

Thus, the limit equals the number (obtained by directly substituting into the reduced expression).