The school bought 20 popular science books and 10 story books, and spent a total of 246.9 yuan. If the price of each popular science book is equal to the price of each story book, find the unit price of these two books. (solution by equation)
学校买了20本科普读物和10本故事书，共花了246.9元，如果每本科普读物与每本故事书的价格相等，求这两种书的单价．(用方程解)
<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">246.9 / 30</gadget>
<output>8.23</output>

<result>8.23</result>