There are two water injection pipes in a pool. It takes 15 minutes to fill the pool with only pipe A and only 12 minutes to fill the pool with pipe B. If A and B both turn on the water injection for 2 minutes and then close the water injection pipe of A, how many minutes will it take for the water injection pipe of B to fill the pool?
一个水池有两个注水管，只开甲水管注满水池需15分钟，只开乙水管注满水池需12分钟．如果甲、乙同时打开注水2分钟后，关闭甲注水管，乙注水管还需多少分钟才能注满水池？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/15) + (1/12)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) * 2</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(7/10) / (1/12)</gadget>
<output>42/5 = around 8.4</output>

<result>42/5 = around 8.4</result>