The warehouse needs to ship out a batch of products, and the shipment will be completed in two days. All (3/7) will be shipped out on the first day, which is 120 fewer than the second day. How many pieces are there in this batch?
仓库要运出一批产品，两天运完，第一天运出全部的(3/7)，比第二天少运出120件，这批产品共有多少件？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (3/7) - (3/7)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">120 / (1/7)</gadget>
<output>840</output>

<result>840</result>