A storybook is 11.5 yuan, and the price of a science book is 1.8 yuan less than twice the price of a storybook. How much is a technical book?
一本故事书11.5元，一本科技书的价钱比故事书的2倍少1.8元．一本科技书多少元？
<gadget id="calculator">11.5 * 2</gadget>
<output>23</output>

<gadget id="calculator">23 - 1.8</gadget>
<output>21.2</output>

<result>21.2</result>