It takes Xiao Hong 20 minutes to type a manuscript alone, and Li Dong 30 minutes to type it alone. How many minutes will it take for the two of them to type this manuscript together?
打一份稿件，小红单独打要20分钟，李冬单独打要30分钟，两人合打完这份稿件，需要多少分钟？
<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>1/12 = around 0.083333</output>

<gadget id="calculator">1 / (1/12)</gadget>
<output>12</output>

<result>12</result>