check out my solution

Done. Thanks.

Count the letters, the cases where your function should return true have 3 of one kind and 2 of other.
The one where your function should return false has 3 different letters there.

I do not understand the terms of the problem.
Why this condition ['b', 'b', 'a', 'b', 'a'] is true
This condition ['a', 'a', 'b', 'c', 'b'] is is false
And this condition ['c', 'a', 'c', 'a', 'c'] is true