Do you mean plagiarism? If you do then copying or stealing could be a synonym
the second bit is more formal, " You're six years old, aren't you?"
because, the other sounds very demanding or imperative, like as if you have to answer the question. so, it has to be the second line.
It is a hundredths place decimal so put it over 100
89/100
since 89's only factors are 1 and 89, you can't simplify, so leave it as it is
