Do u mean the inverse ?
f-^1(x)=3/x-4
It is c. Because the original slope is -3 and perpendicular is opposite. So the perp slope is 1/3. C is the answer.
Say the original price is x
x*[(100-30)/100]=101.50
now solve it
x= 101.50*100/70
Slope = change in Y / change in x
Slope = (-2 - -2) / (-9 - -1)
Simplify:
Slope = 0/-8 = 0
Slope = 0