Answer: if you take 2,000- (-3,500) you get 5,500 ft, making this the distance. Also, think about it this way 2,000 is 2,000 ft from 0, and then there is another 3,500 past zero, putting these together makes the amount of space they are away from each other in total.
Note that when subtracting a negative it becomes positive, using the keep change change rule 2,000 - (-3,500) becomes 2,000 + 3,500