The two masters and apprentices work together to process a batch of parts. It is known that the ratio of work efficiency between the master and the apprentice is 5:7. When the task is completed, the master does 120 fewer parts than the apprentice. How many parts are there in this batch? (two ways to answer)
师徒二人共同加工一批零件，已知师傅与徒弟的工作效率的比是5：7，完成任务时，师傅比徒弟少做120个．这批零件共有多少个？(两种方法解答)
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(5/7) * 120</gadget>
<output>600/7 = around 85.714286</output>

<gadget id="calculator">1 - (5/7)</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(600/7) / (2/7)</gadget>
<output>300</output>

<gadget id="calculator">300 + 120 + 300</gadget>
<output>720</output>

<result>720</result>