Let's address your questions one by one.
Question 6
The most effective way to combine sentences 8 and 9 is:
He would retell the stories he had heard to his young friends, simplifying the language and expressions so they could understand.
This revision is clear, concise, and maintains the original meaning.
Question 7
The most effective revision to make in sentence 12 is:
Lincoln utilized his knowledge of the writings of prominent figures as well as his developed storytelling skills to help shape his platform for president.
This version is clear and logically structured.
Question 8
The redundant idea in the third paragraph (sentences 12–19) that could be deleted is:
Sentence 15
Sentence 15 essentially repeats the idea that Lincoln presented debates and public speeches in the form of stories, which has already been conveyed through earlier sentences.
Question 9
The word "good" in sentence 31 is too vague. A more effective word to use would be:
positive
This word better conveys an inspiring and hopeful tone, fitting the context of Lincoln's communication style.
Please let me know if you need any more help!