Answer
y=2.5x; 30
Work Step by Step
We know direct variation has the equation y=kx. Thus, we plug in the points and solve for k:
$ y=kx \\\\ 7.5=3k \\\\ k=2.5$
We substitute k back in to get the equation: $y=2.5x$
We now plug in x=12:
$y=(2.5)(12)=30$