The engineering team repaired a tunnel, and repaired (1/5) of the full length in the first week, and (7/2) kilometers in the second week, leaving 45% of the total length unrepaired. How many kilometers is this tunnel?
工程队修一条隧道，第一周修了全长的(1/5)，第二周修了(7/2)千米，还剩下全长的45%没修．这条隧道长多少千米？
<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

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

<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (1/5) - (9/20)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">(7/2) / (7/20)</gadget>
<output>10</output>

<result>10</result>