If A and B cooperate to process a batch of parts, it will take 12 days to complete. Now B will process for 3 days, and then A will process for 2 days. The remaining (4/5) of the total number of parts has not been completed. It is known that B processes 4 fewer parts per day than A, how many parts are there in this batch?
加工一批零件，如果甲乙合作需12天完成，现在先由乙加工3天，接着再由甲加工2天后，还剩总数的(4/5)没有完成．已知乙比甲每天少加工4个零件，这批零件有多少个．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/12) * 2</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (4/5) - (1/6)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">(1/30) / 1</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/12) - (1/30) - (1/30)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">4 / (1/60)</gadget>
<output>240</output>

<result>240</result>