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1/2+1/4+1/12+1/24+1/40+1/60+1/84
=(3/4--1/4)+1/4+1/12+(3/24--1/12)+(5/120--2/120)+1/60+1/84
=3/4+3/24+5/120+1/84
=90/120+15/120+5/120+1/84
=11/12+1/84
=77/84+1/84
=78/84
=13/14。