Ronghua Supermarket is open every day from 9:00 am to 8:00 pm. How many hours is it open every day?
榕华超市每天营业时间是上午9：00～晚上8：00，每天营业几小时？
<gadget id="calculator">20 - 9</gadget>
<output>11</output>

<result>11</result>