Greetings from Brasil...
For the composite function f(g(x)), just replace the function g(x) in the x of f(x):
f(x) = 2x - 5
g(x) = 1 + x²
then
f(g(x)) = 2 · (1 + x²) - 5
f(g(x)) = 2 + 2x² - 5
and
f(g(3)) = 2 + 2 · (3)² - 5
