Ineed on all of this pls me i didn't understand how to do this

F(x) is just a synonym for the variable y. So starting with the first problem you must start by subsisting every x that is in the problem. So it will look like this
f(2)=4/2-4
Then you just solve. And your answer will come out to f(2)=-2.

Hope that helped

The density of the cube is 40

U e okay? this question will give me nightmares a lot