To build a highway, team A has built 36% of the total length, team B has built 42% of the total length, and team B has built 4.2 kilometers more than team A. How many kilometers is this highway?
修一条高速公路，甲队修了全长的36%，乙队修了全长的42%，乙队比甲队多修了4.2千米．这条高速公路长多少千米？
<gadget id="calculator">42 / 100</gadget>
<output>21/50 = around 0.42</output>

<gadget id="calculator">36 / 100</gadget>
<output>9/25 = around 0.36</output>

<gadget id="calculator">(21/50) - (9/25)</gadget>
<output>3/50 = around 0.06</output>

<gadget id="calculator">4.2 / (3/50)</gadget>
<output>70</output>

<result>70</result>