Solving Equations: Word Problems - Examples & Practice

Stephen Queen is a best selling author. A friend of his, Sam, asks Stephen if he could donate some copies of his new book to the school Sam works at. Stephen's newest book is measured to be $7$ by $4$ by $1$ inches. Stephen arranges the books in a box with dimensions $21$ by $20$ by $x$ inches. The cost to ship an object with the book's weight is $39$ cents. If it cost $\$35.10$ to ship the box to Sam, what was the height of the box? For simplicity, assume Stephen laid the books flat.