An auditorium has 21 rows of seats. the first row has 18 seats and each suceeding row has two more seats than the previous row. how many seats are in the auditorium?

Quick! a survey of 57 customers was taken at a bookstore regarding the types of books purchased. the survey found that 33 customers purchased mysteries, 25 purchased science fiction, 18 purchased romance novels, 12 purchased mysteries and science fiction, 9 purchased mysteries and romance novels, 6 purchased science fiction and romance novels, and 2 purchased all three types of books. a) how many of the customers surveyed purchased only mysteries? b) how many purchased mysteries and science fiction, but not romance novels? c) how many purchased mysteries or science fiction? d) how many purchased mysteries or science fiction, but not romance novels? e) how many purchased exactly two types of books?

Lena draws a square with an area that is greater than the area of rectangle b. what are two possible side lengths of lena's square? explain.

For a school science project, john noted the temperature at the same time every day for one week. the high temperature for the week was 27°f, and the low temperature for the week was −3°f. what is the difference between the high and low temperatures john recorded?