# Which is the direct linear variation equation for the relationship given y varies directly with x and y = 12 when x = 3?

Jul 4, 2016

$y = 4 x$

#### Explanation:

For a direct linear variation equation
$\textcolor{w h i t e}{\text{XXX}} y = k \cdot x$ for some constant $k$

Given $y = 12$ when $x = 3$
we have
$\textcolor{w h i t e}{\text{XXX}} 12 = k \cdot 3$

$\Rightarrow k = 4$

and the equation is
$\textcolor{w h i t e}{\text{XXX}} y = 4 x$