A project can be completed in 12 days by the cooperation of teams A and B, and it takes 30 days for team B to complete it alone. How many days does it take Team A to complete it alone?
一项工程，甲、乙队合作12天可以完成，乙队独做要30天完成．甲队独做要多少天完成？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/12) - (1/30)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / (1/20)</gadget>
<output>20</output>

<result>20</result>