Answer
$y=0.4x$ (see graph)
Work Step by Step
We are given the ordered pair $(12.5,5)$ which verifies a direct variation relationship. Let's write the equation defining the direct variation:
$$y=kx.$$
In order to determine the relationship we first calculate the constant $k$ by plugging in $x=12.5$ and $y=5$:
$$12.5k=5\Rightarrow k=\dfrac{5}{12.5}=0.4.$$
The equation of variation is:
$$y=0.4x.$$
Graph the equation taking two points: $(0,0)$ and $(12.5,5)$:
