二分之一加六分之五减十二分之七加二十分之九减三十分之十一加四十二分之十三减五是多少?

1/2+5/6-7/12+9/20-11/30+13/42-5
=6/12+10/12-7/12+9/20-11/30+13/42-5
=9/12+9/20-11/30+13/42-5
=15/20+9/20-11/30+13/42-5
=24/20-11/30+13/42-5
=36/30-11/30+13/42-5
=25/30+13/42-5
=35/42+13/42-5
=48/42-5
=8/7-35/7
=-27/7