A) 18-6÷2
B) 4 (9+1) ÷ 2 (6)
C) -2 (3+4)
4

What is the quadric regression equation that fits these data

Could somebody me with this radical simplification?

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?