Take one step at a time. First, let's evaluate g(1):
g(1) = 2*1-3 = -1
now plug this into f:
f(-1) = 5*-1 = -5. So the second answer is the right one.
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Same approach for q 12, only now we have no value to fill in for x. What's confusing here is that the x's of f and g should not be mixed up. For the sake of clarity let's rewrite f as
f(z) = 5z + 9.
Now we'll write 3-4x everywhere we find a z. Ah, only one place.
f(g(x)) = 5(3-4x) + 9 = 15 - 20x + 9 = 24 - 20x