#### Answer

$x=\frac{1}{2}arctan(\frac{y}{3})$

#### Work Step by Step

$y=3tan2x$
Need to solve $x$ in order to find this divide the above equation by 3 both sides.
$tan2x=\frac{y}{3}$
Now, isolate $x$ as follows:
$2x=arctan (\frac{y}{3})$
$x=\frac{1}{2}arctan(\frac{y}{3})$