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 ?
"9 x + 6 y = 20 9 x + 8 y = 30 subtracting 1 from 2 - 2 y = - 10 y = 5 therefore x = 1.1 difference in price = 3.9 d"
divide(subtract(30.00, negate(multiply(8, divide(subtract(multiply(20.00, const_4), multiply(30.00, const_2)), subtract(multiply(6, const_4), multiply(8, const_2)))))), 9)