During the "October" National Day, my father and mother took Xiaoming to the park to buy tickets and share 28 yuan. It is known that the price of one adult fare is equal to the price of three children's fares. How much is an adult ticket.
"十一"国庆节时，爸爸、妈妈带小明游公园买门票共用去28元．已知一张大人票价与三张小孩票价相等．一张大人票多少元．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<gadget id="calculator">28 / 7</gadget>
<output>4</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<result>12</result>