There is a barrel of beverage, A can drink it for 15 days by himself, if he can drink it with B for 10 days, how many days can B drink alone.
有一桶饮料，甲一人饮可以喝15天，若和乙同饮可以喝10天，则乙独饮可以喝多少天．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) - (1/15)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<result>30</result>