Ответ:

9х - 9 = х + 15

9х - х = 15 + 9

8х = 24

х = 24 : 8

х = 3

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11х + 14 - 5х + 8 = 25

6х + 22 = 25

6х = 25 - 22

6х = 3

х = 3 : 6

х = 0.5

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12 - 4х + 12 = 39 - 9х

24 - 4х = 39 - 9х

-4х + 9х = 39 - 24

5х = 15

х = 15:5

х = 3

Verified answer

[tex]\displaystyle\bf\\1)\\\\9(x-1)=x+15\\\\9x-9=x+15\\\\9x-x=15+9\\\\8x=24\\\\x=24:8\\\\\boxed{x=3}\\\\\\2)\\\\(11x+14)-(5x-8)=25\\\\11x+14-5x+8=25\\\\11x-5x=25-14-8\\\\6x=3\\\\x=3:6\\\\\boxed{x=0,5}\\\\\\3)\\\\12-4(x-3)=39-9x\\\\12-4x+12=39-9x\\\\-4x+9x=39-12-12\\\\5x=15\\\\x=15:5\\\\\boxed{x=3}[/tex]