(x+(x-9))-(x-9)=12

Solution for (x+(x-9))-(x-9)=12 equation:

Simplifying
(x + (x + -9)) + -1(x + -9) = 12

Reorder the terms:
(x + (-9 + x)) + -1(x + -9) = 12

Remove parenthesis around (-9 + x)
(x + -9 + x) + -1(x + -9) = 12

Reorder the terms:
(-9 + x + x) + -1(x + -9) = 12

Combine like terms: x + x = 2x
(-9 + 2x) + -1(x + -9) = 12

Remove parenthesis around (-9 + 2x)
-9 + 2x + -1(x + -9) = 12

Reorder the terms:
-9 + 2x + -1(-9 + x) = 12
-9 + 2x + (-9 * -1 + x * -1) = 12
-9 + 2x + (9 + -1x) = 12

Reorder the terms:
-9 + 9 + 2x + -1x = 12

Combine like terms: -9 + 9 = 0
0 + 2x + -1x = 12
2x + -1x = 12

Combine like terms: 2x + -1x = 1x
1x = 12

Solving
1x = 12

Solving for variable 'x'.

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

Divide each side by '1'.
x = 12

Simplifying
x = 12