Question

-7х + 12 = -9х + 54
Решение?

Answer 1

-7х + 12 = -9х + 54

-7х + 9х = 54 - 12

2х = 42

х = 42 / 2

х = 21

Answer 2

Решение:

$-7x+12=-9x+54 \\ \\ -7x+9x=-12+54 \\ \\ x\cdot\Big(-(7-9)\Big)=-(12-54) \\ \\ x\cdot\Big(-(-2)\Big)=-(-42) \\ \\ 2x=42 \\ \\ x=42:2 \\ \\ \boxed{x=21}$

Ответ: $\Large { \boxed { x=21}}$