the answer should be 15 because, if one cup is 120 calories or 8 fluid ounces is 120 calories, divide 120 by 8 so you can find how many calories one fluid ounce is.
The y-intercept is where the graph crosses the y-axis when x = 0. Since you are given the graph, you can see that when x = 0, the graph crosses y = 4, so our y-int is (0, 4).