Answer: 571
To get this answer, we first need to compute the value of f(4). This happens when we plug x = 4 into f(x)
f(x) = 5x + 4
f(4) = 5*4+4 ... each x replaced with 4
f(4) = 20+4
f(4) = 24
Now replace every 'x' in g(x) with f(4) like so
g(x) = x^2 - 5
g(x) = ( x )^2 - 5
g(f(4)) = ( f(4) )^2 - 5 .... every x replaced with f(4)
g(f(4)) = ( 24 )^2 - 5 ... see note below
g(f(4)) = 576 - 5
g(f(4)) = 571
note: the f(4) on the right hand side of that equation is replaced with 24, because we found earlier that f(4) = 24. In other words, f(4) is the same as 24.
