Chapter 8.3, Problem 50MS

Random pitch. During a practice game, your baseball coach decides to choose the pitcher at random from all the players on the team, not just the pitching staff. He chooses your starting left fielder, nicknamed Wild Walter, who has a great arm for distance but not much control. Walter throws 80 pitches: x are strikes, $3x$ are balls (caught by the catcher), and $x-5$ are wild pitches (too wild for the catcher to catch). During this outing on the mound, what’s the probability Walter threw a strike?