500
If my friend Julia is making posters and flyers to announce her as a candidate for student council, and she has poster board for 8 posters and paper for 30 flyers, I would describe her numbers as 8p + 30f. These are the two variables in that expression, as well as what they represent.
The variables are "p" and "f" and they stand for the number of posters and the number of flyers.