Some handicrafts are completed by students A, B, and C. A does 40% of the total, B does 1/4 of the total, and A does 20 more than C. How many pieces are there in this batch of handicrafts?
一些手工作品，由甲、乙、丙三个同学来完成，甲做了总数的40%，乙做了总数的(1/4)，甲比丙多做20个．这批手工作品共有多少件？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (2/5) - (1/4)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">(2/5) - (7/20)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">20 / (1/20)</gadget>
<output>400</output>

<result>400</result>