Answer
$x=3$ $arcsin(-y)$
Work Step by Step
$y=-sin\frac{x}{3}$
Need to solve $x$ in order to find this multiply the above equation by -1 both sides.
$-y=sin\frac{x}{3}$
Apply definition of arcsine.
$\frac{x}{3}=arcsin(-y)$
$x=3$ $arcsin(-y)$
