Question 1198317
.
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.
~~~~~~~~~~~~~~~~


<pre>
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.    <U>ANSWER</U>
</pre>

Solved, with full explanations.