Xiaoyu has 12.4 yuan, Xiaofang has 9.8 yuan, and the difference between them buying a book is 2.1 yuan. How much is the price of this book?
小宇有12.4元，小方有9.8元，两人合买一本书还差2.1元，这本书售价多少元？
<gadget id="calculator">12.4 + 9.8 + 2.1</gadget>
<output>24.3</output>

<result>24.3</result>