It takes 12 days for team A to build a road with a length of 60 km, and it takes 20 days for team B to build it alone. How many days will it take for the two teams to work together to complete the road? (calculated in two ways)
修一条长60千米的公路，甲队单独修需要12天完成，乙队单独修需要20天完成．两队合作需要几天才能修完这条路？(用两种方法计算)
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/12) + (1/20)</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">1 / (2/15)</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>