For a batch of parts, Xiaohua finished on the first day (1/5), on the second day (1/6), and on the third day was the total of the previous two days, what percentage of this batch of parts is left unfinished ．
一批零件，小华第一天完成(1/5)，第二天完成(1/6)，第三天完成的是前两天的总数，问这批零件还剩几分之几没有完成．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/5) + (1/6)</gadget>
<output>11/30 = around 0.366667</output>

<gadget id="calculator">1 - (11/30) - (11/30)</gadget>
<output>4/15 = around 0.266667</output>

<result>4/15 = around 0.266667</result>