Note that the sum of the first n positive integers is
n (n + 1) / 2
For the first one we have this :
Total Profit =
1300 + 150 ( 1 + 2 + 3 +....+ 10 + 11) =
1300 + 150 [ 11 (12)] /2 =
1300 + 75 * (132) =
$11200
The second is easier
The number of seats is given by
(33 + 10) * (n/2) where n is the number of rows = 24 and the last row has 33 seats
(43) (24/2) =
43 * 12 =
516 seats