The range is the set of outputs of a relation or function. In other words, it's the set of possible y values. Recall that ordered pairs are of the form (x,y) so the y coordinate is listed after the x. The output is listed after the input. The output values are y = 3, y = 3, y = 3, y = 5, y = 7. So we simply list these outputs without the "y=" portion. Toss out any duplicates. Only write the unique output values.
The curly braces surrounding the list of values tells us that we have a set.
