At a glance, Kendra believes that the function represented on the graph is linear. How can Kendra determine if the function is actually linear?

She can check to see if the rate of vertical increase equals the rate of horizontal increase between each pair of points.
She can check to see if the sum of each y-value and x-value in every ordered pair is the same.
She can check to see if the quotient of each y-value and x-value in every ordered pair is the same.
She can check to see if the rate of change between the first two ordered pairs is the same as the rate of change between the first and last ordered pairs.

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?