1-(13/42-11/30+9/20-7/12+5/6-1/2)
= 1-13/42+11/30-9/20+7/12-5/6+1/2
= 1-(1/6+1/7)+(1/5+1/6)-(1/4+1/5)+(1/3+1/5)-(1/2+1/3)+1/2
= 1-1/6-1/7+1/5+1/6-1/4-1/5+1/3+1/5-1/2-1/3+1/2
= 1-1/7-1/4+1/5
=1-20/140-35/140+28/140
=1-27/140
=113/140
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