suppose that walmart offers of all diaper purchases in exchange for paying annually to join their diaper club, and that this reduces the price of a package of diapers that usually sells for to . if you join the diaper club, then the equation describes the cost of buying boxes of diapers in one year. on the other hand, if you choose not to join the diaper club, then the equation describes the total cost of buying boxes of diapers in a year. together, these equations define a system of equations.