Xiaojun gets up at 6:00 in the morning and goes to bed at 9:00 in the evening. How many hours does he sleep every day?
小军每天早上6：00起床，晚上9：00睡觉，他每天睡多少小时．
<gadget id="calculator">24 - 21</gadget>
<output>3</output>

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

<result>9</result>