Answer
$x+2y=12$
Work Step by Step
Using $y-y_1=m(x-x_1)$ or the Point-Slope Form of linear equations, the equation of the line with the given conditions,
\begin{align*}\require{cancel}
y_1&=
6
,\\x_1&=
0
,\\m&=
-0.5
,\end{align*}
is
\begin{align*}\require{cancel}
y-6=-0.5(x-0)
\end{align*}
In the form $Ax+By=C,$ the equation above is equivalent to
\begin{align*}
y-6&=-0.5x
\\\\
y-6&=-\dfrac{1}{2}x
\\\\
2(y-6)&=\left( -\dfrac{1}{2}x \right)2
\\\\
2y-12&=-x
\\
x+2y&=12
\end{align*}
