To complete a project, it will take 12 days for team A to complete the project alone, and 6 days for team B to complete the project alone. If A and B cooperate, how many days can they complete?
要完成一项工程，甲队单独完成这项工程要12天，乙队单独完成这项工程要6天，如果甲乙合作，多少天能完成？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/12) + (1/6)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / (1/4)</gadget>
<output>4</output>

<result>4</result>