The workshop arranged for Master Zhang to make a batch of parts. Master Zhang completed the task (4/7) on the first day, and completed the rest (3/5) on the second day. At this time, there were still 30 parts left unfinished. How many are there?
车间安排张师傅做一批零件，张师傅第一天完成了任务的(4/7)，第二天又完成了余下的(3/5)，这时还有30个没做，这批零件一共有多少个？
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 - (4/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/7) * (3/5)</gadget>
<output>9/35 = around 0.257143</output>

<gadget id="calculator">1 - (4/7) - (9/35)</gadget>
<output>6/35 = around 0.171429</output>

<gadget id="calculator">30 / (6/35)</gadget>
<output>175</output>

<result>175</result>