Answer
$y=\dfrac{7}{3}x$
(see graph below)
Work Step by Step
Since $y$ varies directly as $x,$ then it follows the model $y=kx.$ Solving for $k$ by substituting the given point, $(
-3,-7
),$ results to
\begin{array}{l}\require{cancel}
y=kx
\\
-7=k(-3)
\\
\dfrac{-7}{-3}=k
\\
k=\dfrac{7}{3}
.\end{array}
Hence, the direct variation equation is $
y=\dfrac{7}{3}x
.$
Using a table of values, the graph of $
y=\dfrac{7}{3}x
$ is shown above.