A project is done alone. Team A will complete it in 10 days, and Team B will complete it in 15 days. Now after the two teams have cooperated for several days, team B leaves for some reason, leaving team A to work alone until the project is completed. It is known that it took 8 days from start to finish. Ask: How many days did Team B work on?
一项工程，单独来做，甲队要10天完成，乙队要15天可以完成．现在两队合作若干天后，乙队因故离开，留下甲队独自做，直到完工．已知从开工到完成一共用了8天，问：乙队做了多少天？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 8</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">(1/5) / (1/15)</gadget>
<output>3</output>

<result>3</result>