ANSWER
a) Profit = 12n - 275
b) 124 people
Step-by-step explanation
There are 800 seats in the Theater.
Each seat costs $12.
The owners have to pay the performers $275.
a) We want to predict the owners profit for n people that buy tickets.
We know that the owner already loses $275 for paying the performers and he gains $12 for each seat.
If there are n people in a performance, the amount generated from tickets will be:
12 * n = $12n
We also know that Profit is given as:
Profit = Sales - Cost
In this case, the sales is the amount gotten from tickets and the cost is the amount spent on performers.
Therefore:
Profit = 12n - 275
b) The profit is given to be $1213 and we want to find the number of people that attended, that is:
1213 = 12n - 275
=> 1213 + 275 = 12n
=> 12n = 1488
n = 1488 / 12
n = 124 people
124 people attended.