It takes 15 days for team A to complete a certain project alone, and 20 days for team B to do it alone. Now it is required to complete in 12 days, how many days should Team B cooperate with Team A at least.
完成某工程甲队单独做需要15天，乙队单独做需要20天．现在要求12天完成，乙队至少要与甲队合做多少天．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 12</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(2/5) / (1/15)</gadget>
<output>6</output>

<result>6</result>