For a 20-kilometer canal, 25% of the total length was dug on the first day, and 20% of the total length was dug on the second day. How many kilometers are left to be dug?
一条20千米的水渠，第一天挖了全长的25%，第二天挖了全长的20%，还剩下多少千米没挖？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/4) - (1/5)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">20 * (11/20)</gadget>
<output>11</output>

<result>11</result>