Dr. Li started to work the night shift at 8:00 p.m. and left work at 7:00 a.m. the next morning. How many hours did he work in total?
李医生晚上8时开始上夜班，第二天早上7时下班，他一共工作多少小时
<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<gadget id="calculator">4 + 7</gadget>
<output>11</output>

<result>11</result>