Answer
$ln(3x)$
Work Step by Step
We know that $ln(x)$ is a natural logarithm with an understood base of $e$.
Therefore, $ln(x)+ln(3)=log_{e}x+log_{e}3$.
Based on the product rule of logarithms, we know that $log_{b}(MN)=log_{b}M+log_{b}N$ (for $M\gt0$ and $N\gt0$).
Therefore, $log_{e}x+log_{e}3=log_{e}(x\times3)=log_{e}3x=ln(3x)$.