Đáp án+Giải thích các bước giải:

`a:)`

`1/5:1/10-1/3(6/5-9/4)`

`=1/5.10-1/3(24/20-45/20)`

`=2-1/3(-21/20)`

`=2+7/20`

`=47/20`

`b:)`

`1/5(1/2-7/4)-3/4(1/3-11/12)`

`=1/5(2/4-7/4)-3/4(4/12-11/12)`

`=1/5(-5/4)-3/4(-7/12)`

`=-1/4+7/16`

`=3/16`

`c:)`

`25/77.(1/5-7/15):10/11:(-3/4)`

`=25/77.(3/15-7/15):10/11:(-3/4)`

`=25/77.(-4/15).11/10.(-4/3)`

`=-20/231.11/10.(-4/3)`

`=-22/231.(-4/3)`

`=8/63`

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