Answer: 3/5
Step-by-step explanation:
First, you need to find the inverse of f(x)=2x+5 .

Then, you'd plug in 8 into that equation, which I got 
Hope this helps :)
Yes it is the solution to the system
V ≈ 15.63cm^3
volume of a cube = side × side × side = units^3
Volume = 2.5*2.5*2.5 = 15.63^3
<em>Hoped this helped!</em>