For a project, team A worked alone for 20 days, and team B worked alone for 30 days. After a few days of cooperation, B was called out due to another task, and A continued to work. It took 18 days. How many days did team B call out?
一项工程，甲队单独做20天，乙队单独做30天，在合作若干天后，乙因另有任务调出，甲接着干，共用18天，乙队调出了几天？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 18</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/10) / (1/30)</gadget>
<output>3</output>

<gadget id="calculator">18 - 3</gadget>
<output>15</output>

<result>15</result>