An exercise book is 1.5 yuan, a story book is 4.7 yuan, how much more expensive is a story book than an exercise book.
一本作业本1.5元，一本故事书4.7元，故事书比作业本贵多少元．
<gadget id="calculator">4.7 - 1.5</gadget>
<output>3.2</output>

<result>3.2</result>