bài 1 tìm x biết a) 5(x+7)-10=23.5 b) 125-5(4+x)=15 c) 72-7(13-x)=16 d) 26+(5+x)=34

`a) 5(x + 7) - 10 = 23 . 5`

`=> 5(x + 7) - 10 = 115`

`=> 5(x + 7) = 115 + 10`

`=> 5(x + 7) = 125`

`=> x + 7 = 125 : 5`

`=> x + 7 = 25`

`=> x = 25 - 7`

`=> x = 18`

Vậy `x = 18`

`--------------`

`b) 125 - 5(4 + x) = 15`

`=> 5(4 + x) = 125 - 15`

`=> 5(4 + x) = 110`

`=> 4 + x = 110 : 5`

`=> 4 + x = 22`

`=> x = 22 - 4`

`=> x = 18`

Vậy `x = 18`

`-------------`

`c) 72 - 7(13 - x) = 16`

`=> 7(13 - x) = 72 - 16`

`=> 7(13 - x) = 56`

`=> 13 - x = 56 : 7`

`=> 13 - x = 8`

`=> x = 13 - 8`

`=> x = 5`

Vậy `x = 5`

`-------------`

`d) 26 + (5 + x) = 34`

`=> 5 + x = 34 - 26`

`=> 5 + x = 8`

`=> x = 8 - 5`

`=> x = 3`

Vậy `x = 3`

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