Master Wang needs to process 600 machine parts, 210 of which have been completed, and the rest process 30 per hour, how many hours will it take to complete?
王师傅要加工600个机器零件，已经完成了210个，余下的每小时加工30个，还要多少小时才能完成？
<gadget id="calculator">600 - 210</gadget>
<output>390</output>

<gadget id="calculator">390 / 30</gadget>
<output>13</output>

<result>13</result>