Answer:
b > 3, or D.
Explanation:
Solve for b to get the equation of the inequality.
12b - 15 > 21
Add 15 to both sides.
12b > 36
Divide both sides by 12.
b > 3
Since it is greater than and not greater than and equal to, the initial dot will not be circled, which makes it either C or D.
Since it is greater than 3, it means it will be all values to the right of 3, which makes the answer D.