"The word 'how' cannot be used to form a question that elicits the answer 'the third' in the sentence 'Jefferson was the third president' because English lacks a natural way to phrase such a question." Your Sentence (Corrected & More Natural): "If we want to ask about 'the third' in 'Jefferson was the third president,' we cannot use 'how' to form the question. In other words, 'how' does not naturally lead to the answer 'the third' in this context." Tip: When explaining grammar concepts, aim for clarity and conciseness. Avoid repetition and overcomplicating the sentence structure. Instead of saying "question about 'the third,'" use "ask about 'the third.'"

In this case, the pronoun determiner which would be needed instead of how if you're simply asking which number president he was: "Which number president was Jefferson?" which being used to select from a number of concrete options. This would elicit the response, "the third". How would be used in more open-ended questions such as "how did Jefferson become president?"

Which sentence exactly?