# What is the slope of a line perpendicular to the line 3x - y = 8?

I would write your line in the form $y = m x + c$, where $m$ is the slope, as:
$y = 3 x - 8$
So your line has slope $m = 3$
The line perpendicular to this one will have slope ${m}_{1} = - \frac{1}{m} = - \frac{1}{3}$