There are 6 soldiers in a border post, and they send 2 soldiers to stand guard in turn to defend the frontier of the motherland all the time. From 8:00 pm to 5:00 am the next day, how many hours can each of these soldiers rest on average?
一个边防哨所有6名战士，他们轮流派出2名战士站岗放哨，时时刻刻保卫祖国的边疆，从晚上8点到第二天清晨5点，这些战士平均每人能休息多少小时．
<gadget id="calculator">24 - 20</gadget>
<output>4</output>

<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

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

<gadget id="calculator">24 - 3</gadget>
<output>21</output>

<result>21</result>