(6分之5减7分之3加3分之1减14分之9)除负42分之1
=(5/6-3/7+1/3-9/14)÷1/42
=(5/6+1/3-3/7-9/14)x42
=(7/6-15/14)x42
=(7/6)42-(15/14)42
=49-45
=4