A job can be completed by two people working together in 10 days, and by A alone in 14 days. The two work together for 4 days, and B will do the rest alone. How many days will it take to complete?
一件工作，两人合作10天可以完成，甲单独做14天可以完成．两人合作4天，余下的有乙单独做，还需要几天完成？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 4</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 14</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">(1/10) - (1/14)</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">(3/5) / (1/35)</gadget>
<output>21</output>

<result>21</result>