For this mission, you should calculate the number of combinations that cannot form a complete triangle (including degenerated case, when a+b=c).

This implied to me that the degenerated case is included in the set of combinations that cannot form a complete triangle.

If the degenerated case is to be accepted, it should be specified, e.g.:

(for this task, the degenerated case when a+b=c is considered to be a complete triangle)