Make f(x) = y
y = (15x + 50)/(x + 5)
Swap the x and y and make y the subject again
x = (15y + 50)/(y + 5)
x(y + 5) = 15y + 50
xy + 5x = 15y + 50
xy - 15y = 50 - 5x
y(x - 15) = 50 - 5x
y = (50 - 5x)/(x - 15)
So inverse function f^-1(x) = (50 - 5x)/(x - 15)
Ok, a fun hack
if f⁻¹(a)=b then f(b)=a
so if f⁻¹(7)=b then f(b)=7
to find b, find x such that f(x)=7
7=0.5(3)^x
times both sides by 2 (or divide both sides by 0.5)
14=3^x
take log₃ of both sides

Answer:
1/3
Step-by-step explanation:
The volume of a pyramid is always 1/3 of a prism and the volume of a prism is 3 times the volume of the pyramid