It takes 20 days for team A to process a batch of parts alone, and 30 days for team B to finish it alone. If the two teams process at the same time, how many days can they finish?
加工一批零件，甲队单独完成需要20天，乙队单独完成需要30天，如果两队同时加工，多少天可以完成？
<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>1/12 = around 0.083333</output>

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

<result>12</result>