On Sunday, my father and mother took Xiao Fang to visit the Botanical Garden. The tickets cost 42.5 yuan. It is known that the price of an adult ticket is equal to that of two child tickets. How much is a child ticket?
星期天，爸爸、妈妈带小方去参观植物园，买门票共用去42.5元，已知一张成人票与2张儿童票的票价相等，一张儿童票多少钱？
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">42.5 / 5</gadget>
<output>8.5</output>

<result>8.5</result>