Which equation shows a valid, practical step in solving?

Pls! does anybody know a shortcut for answering these types of questions in the future?

If f(x) = 2x - 6 and g(x) = 3x + 9, find (f - g)(x). a. (f-g)(x) = x + 15 o o b. (f- g)(x) = -x - 15 o c. (f- g)(x) = 5x + 3 o d. (f- g)(x) = -x+3 submit

John read the first 114 pages of a novel, which was 3 pages less than 1/3 of the novel. write an equation to determine the total number of pages (p)(p) in the novel.