You are right about the definition of coterminal angles. They all have the same terminal side.
The practice problems probably (and I'm guessing here) are asking what coterminal angle between 0 and 360 degrees is equivalent to the given angle.
For example: What coterminal angle between 0 and 360 degrees is equivalent to 450 degrees.
Answer: 450 - 360 = 90 degrees
Another answer would be -270 degrees if the range were to be changed to -360 < angle < 360.
Does that help at all? The answer depends upon the range which should be given in the exercise.