The cost of holding a party at a rollerskating rink is a function of n, the number of people in the party. The cost function, C , can be represented with this set of rules:
C(n) = 150 ,0 < n ≤ 12
260, 12 < n ≤ 20
400, 20 < n ≤ 30
The cost of a party with 9 people is $_____
.
The cost of a party with 20 people is $_____
It would help if you proofread your questions before you posted them.
"400, 20 < n ≤ 30" includes everything below 20. Otherwise I would choose the second alternative.
For 9 people, it is between 0 and 12, so ?