Let the weight of a box of cereal be x. Since the weight of a box of cereal can vary by 1/4 of an ounce and still be sold as a full box, the possible weights of boxes of cereal will be in the range 18 - 1/4 =< x >= 18 + 1/4 which gives 17.75 =< x >= 18.25. Therefore, the graph representing the possible weights of boxes of cereal is a number line with a line with thick circular ends starting from the point 17.75 to the point 18.25 on the number line.