It takes 20 days for Team A to complete a project alone, and 30 days for Team B to build it alone. How many days can the two teams work together to complete?
一项工程，由甲队单独完成需要20天，由乙队单独修建需要30天，两队合修多少天就能完成？
<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>