An adult ticket is 6 yuan, and a child ticket is 4 yuan. After buying 4 adult tickets for 52 yuan, how many child tickets can I buy?
一张成人票6元，一张儿童票4元，用52元买了4张成人票后还可以买几张儿童票？
<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">52 - 24</gadget>
<output>28</output>

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

<result>7</result>