A county wants to build a river embankment to prepare for flood control. Engineering team A alone can complete this project in 20 days, and engineering team B can only complete all tasks (1/3) in 10 days alone. If the two teams work together, how many days will it take to complete half of this task?
某县要修建河堤为防洪做准备，甲工程队单独做这项工程20天完成，乙工程队单独做这项工程10天只能完成全部任务的(1/3)．若两队合做，多少天能完成这项任务的一半？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) / 10</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">(1/2) / (1/12)</gadget>
<output>6</output>

<result>6</result>