Answer
45
Work Step by Step
We know that logarithms with base $e$ are natural logarithms, and $ln(x)$ can be written as $log_{e}x$.
Therefore, $15ln(e^{3})=15log_{e}e^{3}$.
We know that for all positive numbers $a$ (where $a\ne1$), and all positive numbers $x$, $y=log_{a}x$ means the same as $x=a^{y}$.
Therefore, $15log_{e}e^{3}=15\times3=45$, because $e^{3}=e^{3}$.