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John paid $118.40 for 40 books and pens. He sold 6 pens.
Then the same number of pens and books left.
Each book costs 80 cents more than each pen. How much did he pay for the books.
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Total books plus pens is 40.
Take off 6 pens from 40 items - you will get 40-6 = 34 pens plus books,
and there is the same number of books and pens in 34 items.
Hence, there were 17 books and 17+6 = 40-17 = 23 pens in the original collection.
Let x be the price for the book, in dollars.
Then the price for the pen is (x-0.8) dollars.
Now write the total money equation
17x + 23(x-0.8) = 118.40.
Simplify and find x
17x + 23x = 118.40 + 23*0.8
40x = 136.8
x = 136.8/40 = 3.42 dollars.
Thus, John paid 17*3.42 = 58.14 for the books. ANSWER
Solved, with full explanations.