b-4[b-3(1-b)]=42

Solution for b-4[b-3(1-b)]=42 equation:

Simplifying
b + -4[b + -3(1 + -1b)] = 42
b + -4[b + (1 * -3 + -1b * -3)] = 42
b + -4[b + (-3 + 3b)] = 42

Reorder the terms:
b + -4[-3 + b + 3b] = 42

Combine like terms: b + 3b = 4b
b + -4[-3 + 4b] = 42
b + [-3 * -4 + 4b * -4] = 42
b + [12 + -16b] = 42

Reorder the terms:
12 + b + -16b = 42

Combine like terms: b + -16b = -15b
12 + -15b = 42

Solving
12 + -15b = 42

Solving for variable 'b'.

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

Add '-12' to each side of the equation.
12 + -12 + -15b = 42 + -12

Combine like terms: 12 + -12 = 0
0 + -15b = 42 + -12
-15b = 42 + -12

Combine like terms: 42 + -12 = 30
-15b = 30

Divide each side by '-15'.
b = -2

Simplifying
b = -2