#### Answer

$WV=12$

#### Work Step by Step

Given that the two triangles are similar, then their corresponding sides are proportional.
$\frac {RT}{WU} =\frac {TS}{WV}$
Substitute in known values (and $x$ for the unknown value...
$\frac {4}{6}=\frac {8}{x}$
Cross Multiply...
$4x=48$
Divide both sides by 4...
$x=12$ or $WV=12$