One project, A alone takes 5 hours, and B alone takes 6 hours. Now B will do it first (2/3), and then they will work together. How many hours will it take to finish?
一件工程，甲独做要用5小时，乙独做要用6小时，现乙先做(2/3)后，两人合做．还要几小时才能完成？
<gadget id="calculator">2 / 3</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 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/5) + (1/6)</gadget>
<output>11/30 = around 0.366667</output>

<gadget id="calculator">(1/3) / (11/30)</gadget>
<output>10/11 = around 0.909091</output>

<result>10/11 = around 0.909091</result>