The question tells you that the total price for FOUR people is $21, and then ask about the cost PER PERSON, meaning that you need to figure out the cost of a singular person. The question tells you that each person pays $1.50 and they also need to pay for a game, which they have given the value to be c. So the you add those two cost together ($1.50 + c) and then multiple it by 4 as the question originally tells you that there are 4 players.
