Kandi's boat travels 20 mph. Find the rate of the river current id she can travel 6 miles upstream in the same amount of time she can go 10nmiles downstream. (Let x = the rate of the current)

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?