When given a function such as h(x) = 3x, the value of h(x) is the y value when graphed. If we are asked to find h(x) at x = 4, all we do is plug 4 in for x.
h(4) = 12
We do the same thing with f(g(x)). First plug x=3 into g(x).
g(3) = -5(3) + 2 = -13
Then plug -13 into f(x)
f(-13) = 2(-13) + 1 = -25
The answer is -25.