you have:
f(x) = 2x
g(x) = 2x² - 1
in order to calculate f(g(3)), first evaluate g(3):
g(3) = 2(3)² - 1 = 2(9) - 1 = 18 - 1 = 17
next, calculate f(17):
f(17) = 2(17) = 34
Hence:
f(g(3)) = 34
