A work alone takes 15 days to complete, and B alone takes 20 days to complete. Now A and B cooperate in 12 days to complete the work. During this period, due to the weather, A rested for 3 days, so how many days did B rest?
一件工作，甲单独做要15天完成，乙独做要20天完成，现在甲、乙合作12天才完工．在这段时间里，因天气原因，甲休息了3天，那么乙休息了多少天？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<gadget id="calculator">(1/15) * 9</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 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(2/5) / (1/20)</gadget>
<output>8</output>

<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<result>4</result>