Answer
$\left( 0,\dfrac{4}{3} \right)$
Work Step by Step
Substituting $x=0,$ then
\begin{array}{l}\require{cancel}
3y+x=4
\\\\
3y+0=4
\\\\
3y=4
\\\\
y=\dfrac{4}{3}
.\end{array}
Hence, the coordinates of the $y$-intercept are $
\left( 0,\dfrac{4}{3} \right)
.$
Using the $y$-intercept, the graph of the given equation is shown above.