Simplifying
12 = -1x + 1

Reorder the terms:
12 = 1 + -1x

Solving
12 = 1 + -1x

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add 'x' to each side of the equation.
12 + x = 1 + -1x + x

Combine like terms: -1x + x = 0
12 + x = 1 + 0
12 + x = 1

Add '-12' to each side of the equation.
12 + -12 + x = 1 + -12

Combine like terms: 12 + -12 = 0
0 + x = 1 + -12
x = 1 + -12

Combine like terms: 1 + -12 = -11
x = -11

Simplifying
x = -11