Answer:
f(5) = 20
Step-by-step explanation:
If you have a function f(x) as you do here, to find the value of f(a) or any value that is inside of the f, substitute that value for all values of x in that equation.
Example:
f(x) = x²
f(a) = a²
For your problem with function
f(x) = 4x,
to find f(5), put 5 in for all values of x in the function.
f(5) = 4(5)
f(5) = 20.
