The construction of a subway has been completed (4/7), just 80 kilometers beyond the midpoint. How long is this subway in kilometers?
修一条地铁，已经完成了(4/7)，刚好超过中点80千米．这条地铁全长多少千米？
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(4/7) - (1/2)</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">80 / (1/14)</gadget>
<output>1_120</output>

<result>1_120</result>