I don’t know if I am supposed to substitute the x variable in f(x) or leave the f(x) the same.

Answer:
I believe the answer would be B.
Step-by-step explanation:
The x on the left side of the chart is what you will plug into the function. For example for 0.
f(0) = [tex]\sqrt{100-0}[/tex]
So you just plug in the x into the function.