A job can be done by A in 12 days and by B in 15 days. The two cooperated, and A was transferred away midway. So 10 days to complete the task. How many days did A work less than B?
一项工作，甲单独做要12天完成，乙单独做要15天完成．两人合作，中途甲被调走了．因此10天才完成任务．甲比乙少做了几天？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/15) * 10</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 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/3) / (1/12)</gadget>
<output>4</output>

<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<result>6</result>