You can work these in your head. If all items were date books, the total would have been $250, but was actually $50 more than that. Adding a calendar to the mix instead of a date book adds $.25 to the order cost. So, to add $50, we need to trade 200 of the date books for calendars. There are 200 calendars and 300 date books in the order. _____ Check 200*.75 + 300*.50 = 150 + 150 = 300.
