(3/9*2/8*1/7+4/10*3/9*2/8*6/7+5/11*4/10*3/9*6/8+6/12*5/11*4/10*6/9)/(3/9*2/8*1/7+4/10*3/9*2/8+5/11*4/10*3/9+6/12*5/11*4/10)

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