job alone takes 5 hours to complete, and B can only complete (2/3) of the job in the same time. Now A and B are working together on this job at the same time, how many hours will it take to complete it?
一件工作，甲单独做要5小时完成，乙用同样的时间只能完成这件工作的(2/3)．现在由甲、乙同时合做这件工作，需要多少小时才能完成？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(2/3) / 5</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">(1/5) + (2/15)</gadget>
<output>1/3 = around 0.333333</output>

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

<result>3</result>