A batch of parts is processed, (2/7) of the total number is processed on the first day, and 2 more parts are processed on the second day than on the first day. At this time, the ratio of the number of processed parts to the number of unprocessed parts is 7:5, which means How many batches of parts are there?
加工一批零件，第一天加工了总数的(2/7)，第二天比第一天多加工2个，这时已加工的与未加工的零件个数的比是7：5，这批零件共有多少个？
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

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

<gadget id="calculator">(7/12) - (2/7) - (2/7)</gadget>
<output>1/84 = around 0.011905</output>

<gadget id="calculator">2 / (1/84)</gadget>
<output>168</output>

<result>168</result>