3-(-9)=x

Solution for 3-(-9)=x equation:

Simplifying
3 + -1(-9) = x

Multiply -1 * -9
3 + 9 = x

Combine like terms: 3 + 9 = 12
12 = x

Solving
12 = x

Solving for variable 'x'.

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

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

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

Add '-12' to each side of the equation.
12 + -12 + -1x = 0 + -12

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

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

Divide each side by '-1'.
x = 12

Simplifying
x = 12