"Happy Paradise" is 26.40 yuan each, and "Math is Really Fun" is 19.70 yuan each. Xiaoli pays the salesperson 50 yuan, how much will she get back for buying these two books?
《开心乐园》每本26.40元，《数学真有趣》每本19.70元．小丽付给营业员50元钱，买这两本书还要找回多少元？
<gadget id="calculator">26.4 + 19.7</gadget>
<output>46.1</output>

<gadget id="calculator">50 - 46.1</gadget>
<output>3.9</output>

<result>3.9</result>