Chapter 2 - Limits - Chapter Review Exercises - Page 94: 15

$\frac{ 1}{6}$

\begin{align*} \lim _{t \rightarrow 9} \frac{\sqrt t -3}{t-9} &= \lim _{t \rightarrow 9} \frac{\sqrt t -3}{(\sqrt t -3)(\sqrt t +3)}\\ &=\lim _{t \rightarrow 9} \frac{ 1}{(\sqrt t +3)}\\ &=\frac{ 1}{(\sqrt 9 +3)}\\ &=\frac{ 1}{6}. \end{align*}