What type of equations could have extraneous solutions?

Which of the fallowing best completes the sequence 12,8,5, a) 1 b) 2 c)4 d)0

The head librarian at the library of congress has asked her assistant for an interval estimate of the mean number of books checked out each day. the assistant provides the following interval estimate: from 740 to 920 books per day. what is an efficient, unbiased point estimate of the number of books checked out each day at the library of congress?

Issof claims that the scale factor is 1/2. which statement about his claim is correct