Two more than four times a number as an expression using x as the variable

Can someone me and plz do the problem

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 private savings 'v' = 0.75s and total savings 's' equals $4.20 billion, solve for public and private savings.