A relay race is 4 miles long. If each runner in the race runs 2/3 mile, how many runners are in the race?

I am not sure but my guess is 2

for this case we have by definition, if two lines are perpendicular, then the product of their slopes is -1.

then, given the following line:

so,

we are looking for m_ {2}:

then, the line is given by:

we find "b" replacing the given point:

finally, the equation is:

option c