The master makes 75 parts per hour for 4 hours, and the apprentice makes 45 parts per hour for 6 hours. How many more parts does the master make than the apprentice?
师傅每小时做75个零件，做了4小时，徒弟每小时做45个零件，做了6个小时，师傅比徒弟多做多少个零件？
<gadget id="calculator">75 * 4</gadget>
<output>300</output>

<gadget id="calculator">45 * 6</gadget>
<output>270</output>

<gadget id="calculator">300 - 270</gadget>
<output>30</output>

<result>30</result>