There are three water injection pipes A, B, and C in the reservoir. If A is opened alone, it will take 18 hours to fill the pool; if B and C are opened together, it will take 9 hours to fill the pool; if A, C are opened together, it will take 10 hours to fill the pool. How many hours does it take for B to fill the pool?
蓄水池有甲、乙、丙三个注水管，如果甲单独开需要18小时注满水池；乙、丙合开需要9小时注满水池；甲、丙合开需要10小时注满水池．则乙单开需要多少小时注满水池．
<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

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

<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(1/10) - (1/18)</gadget>
<output>2/45 = around 0.044444</output>

<gadget id="calculator">(1/9) - (2/45)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / (1/15)</gadget>
<output>15</output>

<result>15</result>