Mom and Dad took Xiaoming to the Great Wall to play. They took a tourist bus to and fro, and saw the ticket price written on the sign. Xiao Ming is 1.34 meters tall. Dad bought a round-trip ticket for 3 people and paid the conductor 100 yuan. How much should the conductor get back? (one-way fare: 12.4 yuan per person, half price for children under 1.4 meters)
爸爸妈妈带小明去长城玩，他们坐旅游汽车往返，看到指示牌上写着票价．小明身高1.34米，爸爸买了3个人的往返票，付给售票员100元，售票员应该找回多少元？(单程票价：12.4元/人，儿童1.4米以下半价)
<gadget id="calculator">12.4 * 2</gadget>
<output>24.8</output>

<gadget id="calculator">12.4 / 2</gadget>
<output>6.2</output>

<gadget id="calculator">24.8 + 6.2</gadget>
<output>31</output>

<gadget id="calculator">31 * 2</gadget>
<output>62</output>

<gadget id="calculator">100 - 62</gadget>
<output>38</output>

<result>38</result>