certain engineering team repaired a road. In the first month, it repaired the full length (1/4), and in the second month, it repaired 21 kilometers, and the remaining (3/5) of the whole road was not repaired. What is the total length of this road in kilometers? ?
某工程队修一条公路，第一个月修了全长的(1/4)，第二月修了21千米，还剩下全程的(3/5)没有修，这条公路全长多少千米？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(1/4) + (3/5)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">1 - (17/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">21 / (3/20)</gadget>
<output>140</output>

<result>140</result>