Verified answer

[tex]x - 21 = 9 - 2x \\ x - 2x = 9 + 21 \\ 3x = 30 \\ x = 10[/tex]

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[tex]9x = 28 + 19 + 2x \\ 9x - 2x = 28 + 19 \\ 7x = 47 \\ x = 6\frac{5}{7} [/tex]

Пошаговое объяснение:

№1

х - 21 = 9 - 2х

х + 2х = 9 + 21

3х = 30

х = 30 : 3

х = 10

9х = 28 + 19 + 2х

9х - 2х = 28 + 19

7х = 47

х = 47 : 7

х = 47/7

х = 6. 5/7