Answer
$3$
Work Step by Step
$\because y = \ln{x} \text{ is equivalent to } x=e^y$
$\therefore y=\ln{e^3} \text{ means } e^y=e^3$
The bases are the same so the two sides will obnly be equal if their exponents are equal.
$\therefore y=3$
Thus, $\ln{e^3} = \boxed{3}$
