A favorite part of visiting an amusement park is the food! Julio owns a popcorn machine and has permission to sell bags of popcorn at All-Around Amusement Park. He always provides a free bag of popcorn to the 28 park workers, and he estimates that 1/3 of all park-goers will buy a bag of popcorn. Write an equation in function notation, where f(x) represents the number of bags of popcorn needed, and x represents the number of park-goers.