Final answer:
The equation 12b+9=12b+11 has no solution because upon simplification it leads to a contradiction, 9 does not equal 11.
Step-by-step explanation:
The equation 12b+9=12b+11 is a linear equation which can be simplified by subtracting 12b from both sides. When we do this, we end up with 9 = 11, which is a contradiction. Since these two numbers are not equal, it implies that there is no value of b that would make this equation true. Therefore, this equation has no solution.