To build a canal, the full length (4/15) was built on the first day, and the full length (2/15) was repaired on the second day compared to the first day, what fraction is left unrepaired?
修一条水渠，第一天修了全长的(4/15)，第二天比第一天多修全长的(2/15)，还剩几分之几没有修？
<gadget id="calculator">4 / 15</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">2 / 15</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">(4/15) + (2/15) + (4/15)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<result>1/3 = around 0.333333</result>