A doorman goes to work at 9:00 p.m. and leaves at 6:00 a.m. the next morning, how many hours does he work
一个门卫晚上9时上班，第二天早上6时下班，他工作的时间是多少小时
<gadget id="calculator">12 - 9</gadget>
<output>3</output>

<gadget id="calculator">3 + 6</gadget>
<output>9</output>

<result>9</result>