Ta có : 

`2/3=(2.2)/(3.2)=4/6`

Vì `4<5` nên `4/6<5/6` 

Vậy `2/3<5/6`

cou xem lại đề:

`a)1/2-1/3`

`=3/6-2/6`

`=1/6`

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`b)1/5-1/7`

`=7/35-5/35`

`=2/35`

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`c)7/9-2/5`

`=35/45-18/45`

`=17/45`

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`d)1/2+1/3`

`=3/6+2/6`

`=5/6`

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`e)2/5+1/4+1/3`

`=24/60+15/60+20/60`

`=59/60`

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`g)17/42+3/7`

`=17/42+18/42`

`=35/42`

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`h|)16/17-12/13`

`=208/221-204/221`

`=4/221`

`6:7=0` dư `6` 

cay nhể:vv

bài gì tính lm ngt cx lm hết r :v

xem lại câu a

`a)7/12+(-5/9)`

`=21/36+(-20/36)`

`=1/36`

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`b)3/7-5/(-6)+3/(-7)`

`=3/7+5/6+(-3)/7`

`=3/7+5/6-3/7`

`=(3/7-3/7)+5/6`

`=0+5/6`

`=5/6`