For a manuscript, it takes 10 days for A to type alone, and 8 days for B to type alone. After the existing A and B fight for 4 days, the rest will be finished by C in 2 days. If it is done by C alone, how many days will it take to complete?
一份稿件，甲单独打需要10天完成，乙单独打需要8天完成．现有甲乙和打4天后，剩下的由丙2天打完．如果由丙单独打，需要几天完成？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/10) + (1/8)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">(9/40) * 4</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) / 2</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / (1/20)</gadget>
<output>20</output>

<result>20</result>