Answer
$\frac{10^{1.3}}{3}$, $6.6509$
Work Step by Step
Based on the definition of the common logarithm, we know that $log(x)=log_{10}x$.
Furthermore, recall that $log_{b}x=y$ is equivalent to the statement $b^{y}=x$ (where $x\gt0$, $y$ is a real number, and $b\gt0$ and $b\ne1$).
Therefore, $log(3x)=log_{10}3x=1.3$ is equivalent to $10^{1.3}=3x$.
Divide both sides by 3.
$x=\frac{10^{1.3}}{3}\approx6.6509$