It takes 20 days for teams A and B to complete the repair of a section of road, 30 days for team A to complete the repair alone, and how many days for team B to complete the repair alone.
修一段公路，甲、乙两队合修要20天完成，甲队单独修要30天完成，乙队单独修要多少天完成．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) - (1/30)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">1 / (1/60)</gadget>
<output>60</output>

<result>60</result>