Xiaodong buys two books, one for 68.5 yuan and the other for 19.8 yuan. Xiaodong paid 2 pieces of 50 yuan, how much should the salesperson get back?
小冬买两本书，一本68.5元，另一本19.8元．小冬付了2张50元，售货员应该找回多少元？
<gadget id="calculator">100 - 88.3</gadget>
<output>11.7</output>

<result>11.7</result>