Help me with this please! I don’t understand

The triangles are similar. what is the value of x? x=

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?  

Leslie started last week with $1200 in her checking account. during the week, she wrote the checks below.