Xiaoqiang and Xiaoming buy the same comic book, Xiaoqiang bought 4 books, Xiaoming bought 7 books, Xiaoqiang spent 15 yuan less than Xiaoming, what is the unit price of comic books?
小强和小明买同样的漫画书，小强买了4本，小明买了7本，小强比小明少花15元，漫画书的单价是多少元/本？
<gadget id="calculator">7 - 4</gadget>
<output>3</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<result>5</result>