Perpendicular lines cross each other at a 90° angle. When you know the slope of one, you can find the other line's slope by flipping the first one upside down and making it negative. Since the slope of one of these lines is 3, then the other one will be -[tex] \frac{1}{3} [/tex]. So, the correct answer will be A. -[tex] \frac{1}{3} [/tex].
