A project is completed in 12 days jointly by A and B, team A does it in 3 days, and team B does it in 5 days. To complete the project (19/60), how many days does it take for team A to do the project alone?
一项工程，甲，乙合做12天完成，甲队做3天，乙队做5天，完成工程的(19/60)，甲队单独做这项工程需多少天？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">19 / 60</gadget>
<output>19/60 = around 0.316667</output>

<gadget id="calculator">(1/12) * 3</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(19/60) - (1/4)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">(1/15) / 2</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</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>