Mr. Wang has 58 compositions to correct, and 22 have already been corrected. If 9 papers are graded every hour, how many hours will it take to complete the grades?
王老师要批改58篇作文，已经批改了22篇．如果每小时批改9篇，还要几小时能批完？
<gadget id="calculator">58 - 22</gadget>
<output>36</output>

<gadget id="calculator">36 / 9</gadget>
<output>4</output>

<result>4</result>