A workshop produced a batch of parts in three days. On the first day, it produced 2/7 of the total number. On the second day, it produced 20 more parts than on the first day. On the third day, it produced 55 parts. How many parts are there in this batch?
某车间三天生产了一批零件，第一天生产了总数的(2/7)，第二天比第一天多生产20个，第三天生产了55个．这批零件共有多少个？
<gadget id="calculator">55 + 20</gadget>
<output>75</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7) - (2/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">75 / (3/7)</gadget>
<output>175</output>

<result>175</result>