Can't figure out where to put the parentheses

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?

Which expression gives the exact value of x?

Lmn is an isosceles triangle what is the approximet length of side lm,and what is the approximate perimeter of triangle lmn?