#### Answer

numerator, denominator, $\displaystyle \frac{x+1}{x+3}$

#### Work Step by Step

To simplify a rational expression, we cancel factors that are common to the ___numerator___ and ___denominator___. So, the expression $\displaystyle \frac{(x+1)(x+2)}{(x+3)(x+2)}$ simplifies to $\displaystyle \frac{x+1}{x+3}$ (cancel $x+2$).