It takes 15 days for A and B to process a batch of parts. Now A works alone for 5 days first, and then B works alone for 3 days, and (3/4) of these parts are still unfinished. If A has 4 fewer parts than B every day, how many parts are there in total?
加工一批零件，甲、乙二人合作需15天完成．现由甲先单独工作5天，再由乙单独工作3天后还剩这批零件的(3/4)没完成．若甲每天比乙少4个零件，则这批零件共有多少个．
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(1/15) * 3</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (3/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">(1/20) / 2</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/15) - (1/40) - (1/40)</gadget>
<output>1/60 = around 0.016667</output>

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

<result>240</result>