*This question is very confusing to me. I understand can do normal substitution but word problems are more difficult. *

**The members of the city cultural center have decided to put on a play once a night for a week. Their auditorium holds 600 people. By selling tickets, the members would like to raise $3,900 every night to cover all expenses. Let d represent the number of adult tickets sold at $8.50. Let s represent the number of student tickets sold at **

**$5.50 each. If all 600 seats are filled for a performance, how many of each type of ticket must have been sold for the members to raise exactly $3,900? **

**At one performance there were two times as many student tickets sold as adult tickets. If there were 300 tickets sold at that performance, how much below the goal of $3,900 did ticket sales fall?**