Tính nhẩm

a)456456:1001

Tìm x

(x-15)×8=0

6x-45=27

187:(5x+2)=11

224:(2x-6)=16

`a,`

`456456 : 1001`

`= ( 456 . 1001 ) : 1001`

`= 456 . ( 1001 : 1001 )`

`= 456 . 1`

`= 456`

`---`

`( x - 15 ) . 8 = 0`

`=> x - 15 = 0 : 8`

`=> x - 15 = 0`

`=> x = 0 + 15`

`=> x = 15`

Vậy `x = 15`

`---`

`6x - 45 = 27`

`=> 6x = 27 + 45`

`=> 6x = 72`

`=> x = 72 : 6`

`=> x = 12`

Vậy `x = 12`

`---`

`187 : ( 5x + 2 ) = 11`

`=> 5x + 2 = 187 : 11`

`=> 5x + 2 = 17`

`=> 5x = 17 - 2`

`=> 5x = 15`

`=> x = 15 : 5`

`=> x = 3`

Vậy `x = 3`

`---`

`224 : ( 2x - 6 ) = 16`

`=> 2x - 6 = 224 : 16`

`=> 2x - 6 = 14`

`=> 2x = 14 + 6`

`=> 2x = 20`

`=> x = 20 : 2`

`=> x = 10`

Vậy `x = 10`

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