Question

Identify the italicized clause as a noun clause, an adjective clause, or an adverb clause. He saw how eager she was to do her best. type of clause ______.

Answer 1

If the italicized sentence is how eager she was to do her best, then the answer would be an adverb clause.
Because the whole clause acts as an adverb. 

Answer 2

I think that "how eager she was to do her best." is an adverb clause that show how action accurs and defines verb "saw"