Answer
$\displaystyle \frac{16}{x+7}$
Work Step by Step
When one denominator is the opposite, or additive inverse of the other,
first multiply either rational expression by $\displaystyle \frac{-1}{-1}$
to obtain a common denominator.
$\displaystyle \frac{11}{x+7}-\frac{5}{-x-7}\cdot \displaystyle \frac{-1}{-1} = \displaystyle \frac{11}{x+7}-\frac{-5}{-(-x-7)}$
$= \displaystyle \frac{11}{x+7}-\frac{-5}{x+7} \qquad ... -\displaystyle \frac{-A}{B}=+\frac{A}{B}$
$= \displaystyle \frac{11}{x+7}+\frac{5}{x+7}$
... To add/subtract rational expressions with the same denominator,
add/subtract numerators and place the sum/difference over the common denominator.
= $\displaystyle \frac{16}{x+7}$