There is a class with less than 50 people, among them (4/9) play table tennis, (1/4) run, and the rest play football. How many people play football?
有一个班人数少于50人，其中(4/9)打兵乓球，(1/4)跑步，剩下踢足球，问踢足球的有多少人？
<gadget id="calculator">4 * 9</gadget>
<output>36</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (4/9) - (1/4)</gadget>
<output>11/36 = around 0.305556</output>

<gadget id="calculator">36 * (11/36)</gadget>
<output>11</output>

<result>11</result>