For this case, the first thing we must do is define variables: x: number of pillowcases y: number of sheets We now write the system of equations: 2x + 5y = 40 x = 2y Solving the system we have: x = 8.9 y = 4.4 Answer: The maximum number of pillowcases she could have purchased is: x = 8 (spent less than $ 40)