Put the bacteria A and B in two containers respectively. When the light is bright, it takes 12 hours for bacteria A to divide, and it takes 15 hours for bacteria B to divide; when the light is dark, the division speed of bacteria A will decrease by 40%, and the division speed of bacteria B will increase by 10%. Now two kinds of bacteria start to divide at the same time and finish dividing at the same time. How many hours are there when the light is dark during the division process?
将A、B两种细菌分别放在两个容器里．在光线亮时A细菌需12小时分裂完毕，B细菌需15小时分裂完毕；在光线暗时，A细菌的分裂速度要下降40%，B细菌的分裂速度反而提高10%．现在两种细菌同时开始分裂并同时分裂完毕，试问：在分裂过程中，光线暗的时间有多少小时？
<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 + (1/10)</gadget>
<output>11/10 = around 1.1</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(11/10) - (3/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 / (1/2)</gadget>
<output>6</output>

<result>6</result>