Answer
$A=90$, $B=60$, $C=30$ and $x=4$
Work Step by Step
Since the triangles are similar, then the angles are equal. That is $$A=90, B=60, C=30$$
To find $x$, we set up a ratio between corresponding sides:
$$
\frac{x}{2}=\frac{8}{4}=2\Longrightarrow x=4
. $$