It costs 3.3 yuan to buy a puzzle book, which is as expensive as a fairy tale book. How much does it cost to buy both books?
买一本智力游戏书要3.3元，和童话故事书一样贵．两本书都买需要多少元？
<gadget id="calculator">3.3 + 3.3</gadget>
<output>6.6</output>

<result>6.6</result>