Nanh is really into magic tricks and decides to put on a show to buy more magic trick kits and accessories. She sells three types of tickets to the show. Adult tickets are $10, young adult tickets are $8, and child tickets are $4. Nanh sells a total of 21 tickets and brings in $140. The number of child tickets sold is twice the number of young adult tickets sold. Write a system of equations to represent this situation where x is the number of adult tickets sold, y is the number of young adult tickets sold, and z is the number of child tickets sold. How many of each type of ticket did Nanh sell?  With the $140 she made from the magic show, Nanh now needs to decide what magic tricks she wants to purchase. Small magic kits cost $3 each and larger kits cost $7 each. Nahn wants to buy at least 28 magic kits. Write a system of inequalities to model this situation letting x = the number of small magic kits and y = the number of large magic kits. Then graph the system of inequalities (including all appropriate labels and a scale). Could Nanh purchase 13 small kits and 15 large kits?