Answer
$\lim\limits_{y \to 6}\frac{y+6}{y²-36}$ does not exist.
Work Step by Step
As $\lim\limits_{y \to 6^{-}}\frac{y+6}{y²-36}$ = -$\infty$ $\ne$ $\lim\limits_{y \to 6^{+}}\frac{y+6}{y²-36}$ = +$\infty$, we conclude that $\lim\limits_{y \to 6}\frac{y+6}{y²-36}$ does not exist.
See exercises 21, 22 for work shown on the individual limits.