In order to determine the number of tickets, consider that all money from the sold of tickets, must be at least equal to the total expenses.
If x is the number of tickets sold, the total expenses are:
1,800 + 1,500 + 3.00x
where 3.00x is the expense from the tree bat of each fan (the number of tickets sold is equal to the number of fans)
The money the team earns from tickets and concessions is 7.00x + 1,300, and this quantity must be equal to the total expenses:
7.00x + 1,300 = 1,800 + 1,500 + 3.00x subtract 3.00x both sides
7.00x - 3.00x + 1,300 = 1,800 + 1,500 subtract 1,300 both sides
7.00x - 3.00x = 1,800 + 1,500 - 1,300 simplify like terms
4.00x = 2,000 divide by 4.00 both sides
x = 2,000/4.00
x = 500
Hence, at least 500 tickets must be sold.