(393,393,400,458,482,491,496,507,50 9,511) which two measures of these data best describes the typical number of books that were returned to the library each week?

The mode (number that occurs most often) = 393 since it appears twice in this sequence

the mean (all the numbers added together and divided by the number of numbers in the sequence)= 393 +393 + 400 + 482 + 496 +507 +509 + 511= 3691

the median (when, the numbers are placed in order from lowest to highest, the middle number, or if there is a even amount of numbers, the two middle numbers added together than divided by 2) = 482 + 491 = 973/2 = 486.5

these three terms are all different forms of the average, although once you get to high school you will learn that they may not be very accurate when there is outliers, to which you will learn how to calculate the outliers and how to descaled them form your calculations :)