check the picture below.
if we say, pick a value for the x-coordinate, any value say value "a", and use the 1/5 as the y-coordinate, then,
[tex]\bf \begin{array}{lllll}
&x_1&y_1\\
% (a,b)
&({{ a}}\quad ,&{{ \frac{1}{5}}})
\end{array}
\\\\\\
% slope = m
slope = {{ m}}= \cfrac{rise}{run} \implies 0
\\\\\\
% point-slope intercept
\stackrel{\textit{point-slope form}}{y-{{ y_1}}={{ m}}(x-{{ x_1}})}\implies y-\cfrac{1}{5}=0(x-a)\implies y-\cfrac{1}{5}=0
\\\\\\
y=\cfrac{1}{5}[/tex]
