giúp mik với,giúp mik với !!!

`a ) 4(3x-4) - 2 =18`

`=> 12x - 16 = 18 +2`

`=> 12x - 16 = 20`

`=> 12x = 20 +16`

`=> 12x = 36`

`=> x = 36:12`

`=> x = 3`

Vậy `x = 3`

`b ) B = {x in N | 30 < x ≤ 40}`

`=> x in {31 ; 32 ; 33 ; 34 ; 35 ; 36 ;37 ; 38 ; 39 ; 40}`

Vậy `x in {31 ; 32 ; 33 ; 34 ; 35 ; 36 ;37 ; 38 ; 39 ; 40}`

`c ) (105 - x) : 2^5 = 3^0 +1`

`=> (105 - x) : 32 = 1 +1`

`=> (105 - x) : 32 = 2`

`=> 105 - x = 2.32`

`=> 105 - x = 64`

`=> x = 105 - 64`

`=> x = 41`

Vậy `x = 41`

`d ) 2x - 138 = 2^2 . 3^2`

`=> 2x - 138 = 4.9`

`=> 2x - 138 = 36`

`=> 2x = 36 + 138`

`=> 2x = 174`

`=> x = 174 : 2`

`=> x = 87`

Vậy `x = 87`

`e ) (6x - 39) . 28 = 5628`

`=> 6x - 39 = 5628 : 28`

`=> 6x - 39 = 201`

`=> 6x = 201 + 39`

`=> 6x = 240`

`=> x = 240 : 6`

`=> x = 40`

Vậy `x = 40`

`f ) (9x+2).3 = 60`

`=> 9x +2 = 60 :3`

`=> 9x +2 = 20`

`=> 9x =20-2`

`=> 9x = 18`

`=> x = 18 :9`

`=>x =2`

Vậy `x = 2`

`g ) (26 - 3x) :5 + 71 = 75`

`=> (26 - 3x) :5 = 75 - 71`

`=> (26 - 3x) : 5 = 4`

`=> 26 - 3x = 4.5`

`=> 26 - 3x = 20`

`=> 3x = 26 - 20`

`=> 3x = 6`

`=> x = 6 :3`

`=> x = 2`

Vậy `x = 2`

`h ) 5^(x+1) = 125`

`=> 5^(x+1) = 5^3`

`=> x + 1 = 3`

`=> x = 3-1`

`=> x = 2`

Vậy `x = 2`

`#dtkc`