The students planted 135 trees in total, and 95 have already been planted. If 20 trees are planted every hour, how many hours will it take to finish planting?
同学们去种树，一共要种135棵，已经种了95棵，如果每小时种20棵，还要几小时才能种完？
<gadget id="calculator">135 - 95</gadget>
<output>40</output>

<gadget id="calculator">40 / 20</gadget>
<output>2</output>

<result>2</result>