A project can be completed by team A alone in 45 days and by team B in 60 days. Now Team A and Team B are cooperating, and Team B asks for a few days off for some reason in the middle, and it took 30 days to complete the entire project. Q: How many days off did Team B ask for leave?
一项工程，甲队独做需要45天完成，乙队独做需要60天完成．现在甲、乙两队合作，中途乙队因故请假几天，完成全部工程共用了30天．问：乙队中途请了几天假？
<gadget id="calculator">1 / 45</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">(1/45) * 30</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/3) / (1/60)</gadget>
<output>20</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<result>10</result>