I’m confused with number 1? Can you please explain?

Answer:
1. 15x + 3
Step-by-step explanation:
Given:
f(x) = 3x - 2
g(x) = 12x + 5
You are trying to solve:
f(x) + g(x)
Plug in the coresponding terms to the corresponding variables:
(3x - 2) + (12x + 5)
Combine like terms:
(3x + 12x) + (-2 + 5)
(15x) + (5 - 2)
15x + 3
15x + 3 is your answer.
~