A certain store sells all maps at one price and all books at another price. On Monday the store sold 9 maps and 6 books for a total of $20.00, and on Tuesday the store sold 9 maps and 8 books for a total of $30.00. At this store, how much less does a map sell for than a book?
Choose one: A) $0.25 B) $0.50 C) $0.75 D) $3.9 E) $l.25
9x+6y=20   9x+8y=30   subtracting 1 from 2   -2y=-10   y=5   therefore   x=1.1   difference in price =3.9   $3.9
<result>D</result>
A certain store sells all maps at one price and all books at another price. On Monday the store sold 9 maps and 6 books for a total of $20.00, and on Tuesday the store sold 9 maps and 8 books for a total of $30.00. At this store, how much less does a map sell for than a book?