Master Li needs to make 48 parts, and has already finished 12 parts. If he makes 9 parts per hour, how many hours will it take to complete the task?
李师傅要做48个零件，已经做好了12个，如果每小时做9个，还要几小时能完成任务？
<gadget id="calculator">48 - 12</gadget>
<output>36</output>

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

<result>4</result>