In the winter, rush to repair water conservancy and clean up a 28-kilometer-long canal. The full length (3/7) was cleaned up in the first week, and the rest was cleaned up in the second week. How many kilometers of canals need to be cleaned in the second week?
冬季抢修水利，清理一条长28千米的水渠，第一周清理了全长的(3/7)，余下的第二周清理．第二周需清理多少千米水渠？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (3/7)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">28 * (4/7)</gadget>
<output>16</output>

<result>16</result>