Bài 5: Tìm x, biết: a) 210 -5x =200 b) 210:x-10=20 c) 210-5(x-11)=200 d) (2x+1):7= e) 450:[41-(2x-5)]= f) (5x-9).7+3=80

`210 - 5x = 200`

`=> 5x = 210 - 200`

`=> 5x =10`

`=> x = 10 : 5`

`=> x = 2`

`210:x-10=20`

`=>x-10=210:20`

`=>x-10=210/20`

`=>x-10=21/2`

`=>x=21/2+10/1`

`=>x=21/2+20/2`

`=>x=41/2`

`210 - 5 . ( x - 11 ) = 200`

`=>5 . ( x - 11 ) = 210 - 200`

`=>5 . ( x - 11 ) = 10`

`=>x - 11 = 10 : 5`

`=>x = 2 + 11`

`=>x = 13`

(2x+1):7 `=>` Sai 

450:[41-(2x-5)] `=>` Sai