Answer
$k=\dfrac{7}{2}$
When $k=-0.3,$ $y=-\dfrac{21}{20}$.
Work Step by Step
Since $y$ varies directly as $x,$ then the model equation is $y=kx.$ Using the given values, $
y=7 \text{ and }
x=2
,$ then
\begin{align*}
y&=kx
\\\\
7&=k\left(2\right)
\\\\
\dfrac{7}{2}&=k
.\end{align*}
With the value of $k$ above, the variation equation is $y=
\dfrac{7}{2}
x.$ Substituting $x=-0.3$ in the derived variation equation, then the value of $y$ is
\begin{align*}
y&=\dfrac{7}{2}(-0.3)
\\\\
y&=\dfrac{7}{2}\left(-\dfrac{3}{10}\right)
&\text{ (express $-0.3$ as a fraction)}
\\\\
y&=-\dfrac{21}{20}
\end{align*}
