Giúp mình với ạ , mình cần gấp ạ

Bài 1 , Tìm x :

a) ( 5x - 9 ) . 7 + 3 = 80

b) 400 - 3x = 100

c) 250 : x + 15 = 25

d) 96 - 3. ( x + 8 ) = 42

e) 36 : ( x - 5 ) = 2

`a) ( 5x - 9 ) . 7 + 3 = 80`

`=>  ( 5x - 9 ) . 7 = 80 - 3`

`=> ( 5x - 9 ) . 7 = 77`

`=> 5x - 9 = 77 : 7`

`=> 5x - 9 = 11`

`=> 5x = 11 + 9`

`=> 5x = 20`

`=> x = 20 : 5`

`=> x = 4`

Vậy `x = 4`

`b) 400 - 3x = 100`

`=> 3x = 400 - 100`

`=> 3x = 300`

`=> x = 300 : 3`

`=> x = 100`

Vậy `x = 100`

`c) 250 : x + 15 = 25`

`=> 250 : x = 25 - 15`

`=> 250 : x = 10`

`=> x = 250 : 10`

`=> x=  25`

Vậy `x = 25`

`d) 96 - 3( x + 8 ) = 42`

`=> 3( x + 8 ) = 96 - 42`

`=> 3( x + 8 ) = 54`

`=> x + 8 = 54 : 3`

`=> x + 8 = 18`

`=> x = 18 - 8`

`=> x = 10`

`e) 36 : ( x - 5 ) = 2`

`=> x - 5 = 36 : 2`

`=> x - 5 = 18`

`=> x = 18 + 5`

`=> x = 23`