question: and so it was, that all who fell that day, men as well as women, were twelve thousand, all the people of ai.
Capitalize this past sentence correctly.
A: And so it was, that all who fell that day, men as well as women, were twelve thousand, all the people of Ai.

question: before you can open a s3i file, you'll need to figure out what kind of file the s3i file extension refers to.
Capitalize this past sentence correctly.
A: Before you can open a S3I file, you'll need to figure out what kind of file the S3I file extension refers to.

question: von koch was then appointed to the chair of pure mathematics at the kth.
Capitalize this past sentence correctly.
A: Von Koch was then appointed to the chair of pure mathematics at the KTH.