#### Answer

The constant of variation is $14$.
The direct variation equation is $y=14x$.

#### Work Step by Step

$y=kx$
$y=7; x=\frac{1}{2}$
$7=k(\frac{1}{2})$
$7\times2=k$
$14=k$
The constant of variation is $14$.
The direct variation equation is $y=14x$.