Xiaolan went to the bookstore and bought two books. "Fairy Tale" is 12.5 yuan, and "Science and Technology Small Production" is 3.5 yuan cheaper than "Fairy Tale". How much does Xiaolan pay?
小兰去书店买了两本书．《童话故事》12.5元，《科技小制作》比《童话故事》便宜3.5元．小兰应付多少钱？
<gadget id="calculator">12.5 - 3.5</gadget>
<output>9</output>

<gadget id="calculator">9 + 12.5</gadget>
<output>21.5</output>

<result>21.5</result>