A theater sells adult tickets for $8.00 and children's tickets for $5.50. Sally bought some of each kind (not the same number) and paid a total of $78.50. Which equation represents this situation? A) x + y = 78.5 B) 13.5x = 78.5 C) 13.5xy = 78.5 D) 8x + 5.5y = 78.5