System of Equations: Comic Book Store Deals

Question

A comic book store offers two subscription packages. The first has a $10 monthly fee and $1 per comic. The second has $2 per comic without a monthly fee. When is each plan the better deal?

Answer 1

You can graph both equations where y=total cost and x=number of books, and see where they cross. Prior to crossing is the better deal for one plan, where after they cross is the better deal for the other plan.

You can set the two equations equal to each other and solve for x (number of books). Any number less than x will be best for not have a monthly fee, where any number greater than x will be where you should pay the monthly fee. If you plan on getting x comics, then the plans are the same cost.

x=5. That's where both deals are the same cost. If you want less than 5 comics, do not get the monthly fee; more than 5 is cheaper cost with the fee.