3x+7 = x-1 does x = - 4?

Subtract x from both sides:

(3x - x) + 7 = (x - x) - 1

3x - x = 2x:

2x + 7 = (x - x) - 1

x - x = 0:

2x + 7 = - 1

Subtract 7 from both sides:

2x + (7 - 7) = - 7 - 1

7 - 7 = 0:

2x = - 7 - 1

-7 - 1 = - 8:

2x = - 8

Divide both sides by 2:

2x / 2 = - 8 / 2

2 / 2 = 1:

x = - 8 / 2

The gcd (greatest common denominator) of 8 and 2 is 2:

-8 / 2 = 2 (-4) / 2x1 = 2/2 x - 4 = - 4

x = - 4