One job can be done by A alone in 10 days and by B in 15 days. Now, B does this job first, and after 6 days, A joins in to do it together, and then B takes a day off due to work, how many days does it take for this job from the beginning to the final completion?
一件工作，甲独做10天完成，乙独做15天完成．现在，乙先做这件工作，6天后甲参加进来一起做，后乙因事休息了一天，问这件工作从开始做到最后完工共用多少天？
<gadget id="calculator">6 / 15</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (2/5) - (1/10)</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/2) / (1/6)</gadget>
<output>3</output>

<gadget id="calculator">6 + 3 + 1</gadget>
<output>10</output>

<result>10</result>