Final answer:
Karen is exhibiting reaction formation by tutoring in math and speaking positively about it to combat her unconscious fear of the subject.
Step-by-step explanation:
Karen's behavior of tutoring children in math and expressing enjoyment for it, despite her intense fear of mathematics, is an example of reaction formation. Reaction formation is a defense mechanism where a person behaves in the opposite way to their actual feelings. This is done unconsciously as a way to cope with the anxiety their true feelings cause.
In this scenario, Karen's enthusiastic involvement in math could be seen as an overcompensation for her fear, representing the feelings and behaviors that are contrary to her true underlying fear of mathematics. This contrasts with other defense mechanisms such as repression where distressing thoughts are unconsciously blocked out, or sublimation, where unacceptable impulses are transformed into socially acceptable behaviors.