project is completed in 15 days by A alone, and completed in 10 days by B. After working together for several days, A rests for a few days, and the result is completed in 8 days. How many days does A rest?
一项工程，甲单独做15天完成，乙10天完成，两人合作若干天后，甲休息了几天，结果共用8天完成，求甲休息了几天？
<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>

<gadget id="calculator">8 - 3</gadget>
<output>5</output>

<result>5</result>