Given a line with a slope of -1/5, what is the slope of any lines that lies perpendicular to it?
a. 2/5
b. -5
c. -1/5
d. 5
e. 10
f. 1/5

The answer is 5

If two slopes are perpendicular to one another, their product will be -1.
This can be shown as;
(-1/5) * x = -1
x = (-1)/(-1/5)
x = 5