# Math Textbooks for Sale

Pro Problems > Math > Algebra > Equations > Systems of Equations > Word Problems## Math Textbooks for Sale

The cost of a textbook is directly proportional to the number of math problems it contains, and inversely proportional to the number of authors who wrote the book. A textbook which contains 200 problems, and was written by 3 authors costs $5 less than a textbook which contains 150 problems, and was written by 2 authors. What is the cost of a textbook containing 450 problems, and written by 4 authors?

## Solution

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One king's horse can break a piece in two every 2 seconds.

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