Madelyn and her children went into a movie theater and she bought $39 worth of bags of popcorn and pretzels. Each bag of popcorn costs $6.50 and each pretzel costs $3.25. She bought 4 times as many pretzels as bags of popcorn. Graphically solve a system of equations in order to determine the number of bags of popcorn, x, x, and the number of pretzels, y, y, that Madelyn bought.