Answer
$6$
Work Step by Step
Substitute $\frac{\pi}{6}$ to $x$ to obtain:
$6\sin{(3x)}= 6\sin{[3(\frac{\pi}{6})]}=6\sin{(\frac{\pi}{2})}$
$\dfrac{\pi}{2}$ is a special angle whose sine value is $1$.
Thus, when $x=\frac{\pi}{6}$,
$6\sin{(3x)} = 6 \cdot 1=6$