Which of the following sets represents a function? {(3, 5), (-1, 7), (3, 9)} {(1, 2), (3, 2), (5, 7)} {(1, 2), (1, 4), (1, 6)}

B, since the others have one x going to multiple y's.

Think of functions as someone going down a slide. Multiple people can go down different X slides and land in the same Y position, however one person cannot go down the same X slides and end up in a different Y position.