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

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

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5/2*3-1/则蚂3*4-9/4*5+11/5*6-1/6*7=5/6-（1/3-1/4）-（1/4+1/5）+（穗燃1/5+1/6）-（1/6-1/7）=5/6-1/3+1/4-1/4-1/5+1/5+1/6-1/6+1/7=5/6-1/3+1/7=1/孙族埋2+1/7=9/14

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