Ah, simple!
It's important to identify what each part of your equation, which is in slope intercept form.
Let's break it down:
3x = Slope (in this case, it would be [tex]\frac{3}{1}[/tex], which means to go to the up three units, and right one unit)
-1 = Y-intercept (where your line begins)
If there's any confusion, feel free to leave a comment.