What would cause a relation to be a function?

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?  

If a || b and b | y, then ? a) x || y. b) x | a. c) a | y. d) a || y.

How to write four times a number,minus 6,is equal to theee times the number+8 as an equqtion