Answer: just graph these two equations
option a: y = 5x + 10
option b: y = 7.5x
and then tell at what number of event would having a card and not having a card is cheaper.
Explanation:
the initial cost, $10, is your b value for the equation y = mx + b so yo would start here on the y axis. but for the second option you start at zero since you don't have a b value