a: =>x=2
b: =>x+102=715
=>x=613
c: =>x-203=408
=>x=611
d: =>12-x=5
hay x=7
a. 7x = 14
x = 14 : 7
x = 2
b. ( x + 102 ) - 214 = 501
( x + 102 ) = 501 + 214
( x + 102 ) = 715
x = 705 - 102
x = 603
c. ( x - 203 ) : 4 = 102
( x - 203 ) = 102 x 4
( x - 203 ) = 408
x = 408 + 203
x = 611
d. 3 (12 - x) = 15
(12 - x) = 15 : 3
(12 - x) = 5
x = 12 - 5
x = 7
`a) 7x =14`
`=> x=14/7=2`
Vậy `x=2`
`b) (x+102) -214 =501`
`=> (x+102) = 501 +214`
`x+102 = 715`
`=> x =715 -102 =613`
Vậy `x=613`
`c) ( x - 203 ) : 4 = 102`
`=> x-203 = 102 * 4 `
`x-203 = 408`
`=> x = 408 +203`
`x=611`
Vậy `x=611`
`d) 3 (12 - x) = 15`
`=> 12-x =15/3 `
`12-x = 5 `
`=> x=12-5 =3`
Vậy `x=3`