Using the polynomial remainder theorem you divide the polynomial by a linear polynomial given as x-r, where r is the value of f(x)
You are given the value of f(x) as 4.
So now you have:
x^4 -2x^3+5x^2 -20x-4 / x-4
Divide
= x^3 +2x^2 +13x +32 +124/x-4
The remainder is the number above the x-4, which is 124.
f(4) = 124
