3x - y = 1
First you have to change this into slope intercept form (y = mx + b).
3x - y = 1
-y = -3x + 1
y = 3x - 1
m = 3
(m is the slope)
So the line parallel to this line will also have a slope of 3.
If they waned the perpendicular line though, it would be the negative reciprocal (-1/3).
The answer is 3.