Please help! I need this fast. A music store sells regular CDs for $8.50. On average, the store sells 90 CDs every day. For each 50-cent increase in the price of regular CDs, the sales of CDs will go down by 5. What should the CD price be to get the most income from CD sales?

Solve the problem by making up an equation. a man could arrive on time for an appointment if he drove the car at 40 mph; however, since he left the house 15 minutes late, he drove the car at 50 mph and arrive 3 minutes early for the appointment. how far from his house was his appointment?