Jarrod helped his teachers pack textbooks into boxes for the summer. He packed 6 boxes of science textbooks with 14 books per box. He also packed math textbooks with 12 books per box. If x represents the total number of boxes he packed, which of the following equations can be used to find the total number of books that Jarrod packed into boxes?
A. y = 84(x - 6) + 12
B. y = 12x + 84
C. y = 84x + 12
D. y = 12(x - 6) + 84