Father and mother take Xiao Ming (children) to grandma's house by car. The fare is 18 yuan for adults and half price for children. How much does it cost for three people to buy a round-trip ticket?
爸爸、妈妈带小明(儿童)坐车去奶奶家，成人票价18元，儿童半价．三人往返一次买票共需多少钱？
<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">36 + 9</gadget>
<output>45</output>

<gadget id="calculator">45 * 2</gadget>
<output>90</output>

<result>90</result>