An amusement park charges $3 for an ice cream cone and sells an average of 600 cones per day currently. A survey shows that, for each $1 increase in cost, 75 fewer people would buy a cone. determine the number of cones sold at that maximum revenue
determine the maximum revenue that can be made from the sales of the cones
determine the cone price that would result in maximum revenue

The following relation is not a function

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.