Tingting bought two story books with the same price, paid 50 yuan, and got back 18.6 yuan. How much is the price of each storybook?
婷婷买两本价格相同的故事书，付出50元，找回18.6元．每本故事书的价格是多少元？
<gadget id="calculator">50 - 18.6</gadget>
<output>31.4</output>

<gadget id="calculator">31.4 / 2</gadget>
<output>15.7</output>

<result>15.7</result>