Xiao Ming goes to bed at 9:00 every night and wakes up at 7:00 the next morning. How many hours does Xiao Ming sleep every day?
小明每天晚上9﹕00睡觉，第二天早上7﹕00起床，小明每天睡了多少小时．
<gadget id="calculator">24 - 21</gadget>
<output>3</output>

<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<result>10</result>