I need help. Can someone explain how to do this please. (photo)

Answer:
basically the number inside the 1st f( )of each problem must be plugged into all the it's in its equation an example would be with the first problem:
Step-by-step explanation:
1st:plug in the number inside the f(x) function into all the x's in the equation so #1 would look like this: f(x)=2-4, then solve for x
2nd your solution for #1 would be f(x)=-2