In a shopping mall on the eve of New Year's Eve, the discounted cups with the original price of 3.5 yuan are 80 cents cheaper each. Mom bought 12 of these cups and paid the cashier 50 yuan, how much should the cashier give her mother.
某商场元旦前夕优惠酬宾，原价3.5元的杯子打折后，每个便宜8角钱．妈妈买了12个这样的杯子，付给收银员50元，收银员应找给妈妈多少元．
<gadget id="calculator">3.5 - 0.8</gadget>
<output>2.7</output>

<gadget id="calculator">2.7 * 12</gadget>
<output>32.4</output>

<gadget id="calculator">50 - 32.4</gadget>
<output>17.6</output>

<result>17.6</result>