Answer: 9
Step-by-step explanation:
Stations B and D are both on the y-axis. B is at 2 while D is at -7. Count the number of spaces between the stations to count out 9 spaces.
We move 2 units down to go from B to A. Then another 7 units down to go from A to D. That's a total of 2+7 = 9 units.
It's possible to use the distance formula, but that would be overkill.