#### Answer

The constant of variation is $\frac{3}{2}$.
The direct variation equation is $y=\frac{3}{2}x$.

#### Work Step by Step

$y=kx$
$y=12; x=8$
$12=k(8)$
$\frac{12}{8}=k$
$\frac{3}{2}=k$
The constant of variation is $\frac{3}{2}$.
The direct variation equation is $y=\frac{3}{2}x$.