A piece of work, if A and B alone would take 20 days and 30 days to complete, but now they are working together, because A took a few days off due to illness, it took 15 days to complete it, how many days did A take a break?
一件工作，如果甲、乙单独做分别需要20天和30天完成，现在两人一起合做，由于中间甲因病休息了几天，结果用了15天才完成，问甲休息了几天？
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/30) * 15</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/2) / (1/20)</gadget>
<output>10</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<result>5</result>