6分之5减12分之1减20分之9加30分之11减42分之1简便运算

5/6 -1/12 -9/20 +11/30 -1/42
=5/6 -1/42 -1/12 -9/20 +11/30
=35/42 -1/42 - 5/60 -27/60 + 22/60
=34/42 -10/60
=34/42 -1/6
=34/42 -7/42
=27/42
=9/14