Final answer:
A counterclockwise 270-degree rotation is equivalent to a 90-degree clockwise rotation, which is the correct answer describing this transformation mathematically.
Step-by-step explanation:
The question asks for a rule that describes a counterclockwise 270-degree rotation in mathematical terms. Rotating a point or shape 270 degrees counterclockwise is equivalent to a 90-degree clockwise rotation (Option A) because a full circle is 360 degrees, so subtracting 270 degrees from 360 degrees gives us 90 degrees. Therefore, moving in the opposite direction (clockwise), for the same amount, yields a figure in the same position as if it had been rotated 270 degrees counterclockwise. None of the other options (B: 180-degree counterclockwise rotation, C: 270-degree clockwise rotation, D: 360-degree rotation) describe a transformation that is equivalent to a 270-degree counterclockwise rotation.