You could use a calculator or you could perform long division to find the remainder of 15/266. There is no integer quotient, other than 0 (zero). That means 15 is the remainder.
Supposing you were dealing with 266/15 (which is really a different problem). This division produces an integer quotient and a remainder:
266
------- = 17 r. 11
15
Double-check to ensure that you've copied this problem down correctly.
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: