Answer
The slope is $-\frac{1}{3}$
The y-intercept is $0$
We can see the graph of the line $~~x+3y = 0$:
Work Step by Step
The slope-intercept form of the equation of a line is $~~y=mx+b~~$ where $m$ is the slope and $b$ is the y-intercept.
$x+3y = 0$
$3y = -x$
$y = -\frac{1}{3}x+0$
The slope is $-\frac{1}{3}$
The y-intercept is $0$
We can see the graph of the line $~~x+3y = 0$:
