Question

insert one comma to separate the coordinate adjectives. overcome with emotion, tim immediately embraced his beloved childhood friend. the two spent the next few hours recalling the exciting fun - filled summer afternoons of their youth.

Explanation:

Coordinate adjectives modify a noun equally and can be separated by a comma. "exciting" and "fun - filled" are coordinate adjectives modifying "summer afternoons".

Answer:

Overcome with emotion, Tim immediately embraced his beloved childhood friend. The two spent the next few hours recalling the exciting, fun - filled summer afternoons of their youth.