To solve for b, rearrange the equation by subtracting 12a from both sides:
A - 12a = 12(a + b) - 12a
Simplify:
A - 12a = 12a + 12b - 12a
Combine like terms:
A - 12a = 12b
Finally, divide both sides by 12 to solve for b:
(A - 12a) / 12 = b