She is starting at 4000, so that is the y-intercept of the graph. She is descending at 40 feet per minute, so her rate of change or slope is -40. The graph would look like this:
Looking at your "<span>16 -3/4," I see only one possibility: "combine the following."
</span><span>16 -3/4 is the same as 15 + 4/4 - 3/4, or 15 1/4.
Similarly, 16 - 0.75 = 15.25 = 15 1/4.</span>