A piece of land can be plowed in 5 hours alone, B can be plowed in 10 hours alone, if A and B can plow in 2 hours, and the rest can be plowed by B alone, how long will it take?
一块地甲单耕5小时完成，乙单耕10小时完成，设甲乙合耕2小时，剩下的由乙单耕，还要多久耕完？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">(1/5) + (1/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(3/10) * 2</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

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

<result>4</result>