What does it mean 'what is the value' of a number

Aschool puts on a play. the play costs $1,200 in expenses. the students charge $4.00 for tickets. there will be one performance of the play in an auditorium that seats 500 people. what is the domain of the function that shows the profit as a function of the number of tickets sold?  

Ineed in figuring out this problem.

Which expression shows the sum of the polynomials with like terms grouped together