you buy 20 cupcakes for 25 dollars and your going to sell them for 2 dollars each you want to write an expression that represents how much money you will make each day that you sell cupcakes wich of these quantites should be reperesented with a variable.
the number of cupcakes sold
the number of cupcakes you bought
the amount of money you spent on the cupcakes
the cost of each cupcake sold