Xiao Ming took the train from Jiaozuo to Beijing to visit his grandma. He departed at 21:00 on May 2 and arrived at 8:00 on May 3. How many hours did he pass on the way?
小明乘火车从焦作去北京看望奶奶，5月2日21时出发，5月3日早晨8：00到达，途中共经过了多少小时．
<gadget id="calculator">24 - 21</gadget>
<output>3</output>

<gadget id="calculator">8 - 0</gadget>
<output>8</output>

<gadget id="calculator">3 + 8</gadget>
<output>11</output>

<result>11</result>