bài 1: tìm x a) ( 27 - x ) - 18 = 2 b) 13 - ( x - 7 ) = 12 c) 2 . ( x + 10 ) - 128 : 4 = 0 d) 64 - ( 6 + x) = 40 e) 42 - 3 . ( x - 7 ) = 21 f) 25 - ( x + 3 ) = 20

Đáp án + Giải thích các bước giải:

`a) ( 27 - x ) - 18 = 2`

`27-x = 20`

`x = 27 -20`

`x = 7`

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`b) 13 - ( x - 7 ) = 12`

`x-7 = 13-12`

`x-7 = 1`

`x = 7 + 1`

`x= 8`

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`c) 2 . ( x + 10 ) - 128 : 4 = 0`

`2.(x+10) - 32 =0`

`2.(x+10) = 32`

`x + 10 = 32 :2`

`x + 10 = 16`

`x = 16-10`

`x= 6`

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`64 - ( 6 + x) = 40`

`6+x = 64-40`

`6+x = 24`

`x = 24-6`

`x = 18`

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`42 - 3 . ( x - 7 ) = 21`

`3.(x-7) = 42-21`

`3.(x-7) = 21`

`x-7 = 21:3`

`x-7 = 7`

`x  =7+7`

`x = 14`

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`f) 25 - ( x + 3 ) = 20`

`x+3 = 25-20`

`x+3 = 5`

`x = 5-3`

`x = 2`

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