3[4-(12-7)]=x

Solution for 3[4-(12-7)]=x equation:

Simplifying
3[4 + -1(12 + -7)] = x

Combine like terms: 12 + -7 = 5
3[4 + -1(5)] = x

Multiply -1 * 5
3[4 + -5] = x

Combine like terms: 4 + -5 = -1
3[-1] = x

Multiply 3 * -1
-3 = x

Solving
-3 = 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.
-3 + -1x = x + -1x

Combine like terms: x + -1x = 0
-3 + -1x = 0

Add '3' to each side of the equation.
-3 + 3 + -1x = 0 + 3

Combine like terms: -3 + 3 = 0
0 + -1x = 0 + 3
-1x = 0 + 3

Combine like terms: 0 + 3 = 3
-1x = 3

Divide each side by '-1'.
x = -3

Simplifying
x = -3