A car salesperson kept data on cars he sold over the last few years. For each car he recorded the car's age (x) and car's selling price in $1,000 (y). The line of best fit is y=-1.8x+21.
Interpret the y-intercept in context.

Charlie is at an amusement park that has 18 different rides. each ride costs $1.75. the function c(r) = 1.75r represents the total amount of money that charlie will spend if he goes on r rides, but he never goes on the same one more than once. what domain and range are reasonable for the function?