The master and the apprentice process a batch of parts at the same time, and their work-efficiency ratio is 9:7. When the task is completed, the master processes 80 more parts than the apprentice. How many parts are there in this batch?
师徒二人同时加工一批零件，他们的工效比是9：7，完成任务时，师傅比徒弟多加工80个零件，这批零件有多少个．
<gadget id="calculator">9 - 7</gadget>
<output>2</output>

<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">9 + 7</gadget>
<output>16</output>

<gadget id="calculator">40 * 16</gadget>
<output>640</output>

<result>640</result>