The school bought a total of 55 story books and science books, each story book is 8 yuan, each science book is 15 yuan, and the total cost is 650 yuan. How many story books did you buy?
学校新买故事书和科技书共55本，每本故事书8元，每本科技书15元，共花650元，买故事书多少本？
<gadget id="calculator">55 * 15</gadget>
<output>825</output>

<gadget id="calculator">825 - 650</gadget>
<output>175</output>

<gadget id="calculator">15 - 8</gadget>
<output>7</output>

<gadget id="calculator">175 / 7</gadget>
<output>25</output>

<result>25</result>