If 2 lines (or line segments) are perpendicular, then the product of their slopes is equal to -1.
Thus, since the given line segments are perpendicular, we have:
[tex]\displaystyle{ \frac{1}{3}\cdot \frac{d}{5}=-1 [/tex].
Multiplying both sides of the equation by 15, we get d=-15.
Answer: d=-15
