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Câu `2:` 

`a) 198 - 42 : 6 xx x + 16 = 0`

`19 - 7 xx x + 16 =0`

`7 xx x + 16 = 19`

`7 xx x = 3`

`x = 3/7` 

Vậy `x = 3/7` 

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`b) x xx 3,9 + x : 10 = 26`

`x xx 3,9 + x xx 0,1 = 26`

`x xx (3,9 + 0,1) = 26`

`x xx 4 = 26`

`x = 26 : 4`

`x = 13/2` 

Vậy `x = 13/2` 

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`c) x xx 11 + x : 0,25 = 24`

`x xx 11 + x xx 4 = 24`

`x xx (11 + 4) = 24`

`x xx 15 = 24`

`x = 8/5` 

Vậy `x = 8/5 ` 

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Câu `1 : ` 

`(7,5 xx 18,3 + 26,4 xx 18,3) xx (47 xx 11 - 4700 xx 0,1 - 47)`

`= [(7,5+26,4) xx 18,3] xx (47 xx 11 - 47 xx 10 - 47)`

`= (33,9 xx 18,3) xx [47 xx (11-10-1)]`

`= 620,37 xx [47 xx 0]`

`= 620,37 xx 0`

`= 0`

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`b) 2 2/3 + 5/9 + 4/9 : (30% - 1/10) - 2/9`

`= 8/3 + 5/9 + 4/9 : (3/10 - 1/10) - 2/9`

`= 8/3 + 5/9 : 1/5 - 2/9`

`= 8/3 + 25/9 - 2/9`

`= 8/3 + 23/9`

` = 47/9`

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`c) 1/2 : 0,5 - 1/4 : 0,25 + 1/8 : 0,125 + 2021` 

`= 1 - 1 + 1 + 2021`

`= 0 + 1 + 2021`

`= 1 + 2021`

`= 2022` 

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