Front-row tickets for a concert cost $60. after every 5 rows, the ticket price goes down by $5. what is the total amount of money generated by a full house? info: there are 20 rows that increase by 3 seats each time starting with 18.

I think I got it, but just in case...tell me the whole thing again. I wasn't listening.

N a 20 row theater, the number of seats increases by 3 with each successive row.  The first row has 18 seats.

a. Write an arithmetic series in summation notation to represent the number of seats in the theater,∑n=12018+3(n−1)b. What is the total seating capacity of the theater? 
930 seats

c. Front row seats cost $60.  After every 5 rows, the price drops $5.  What is the amount generated by a full house?
$46950

2.  An arithmetic series has a first term of 4.  The sum of the first 40 terms is 6080.  Find the value of the 40th term?
use the formula
sum of first n terms = n/2 * (s1 + sn) 
6080 = 40/2 * (4 + sn)