Answer:
Scottie = 30
Lighthouse = ? (can't see height in image)
The boat = 0
The fish = -10
Distance between Scottie and fish = 40
Reason:
It starts off by saying that Scottie is 30 meters above, so that is solved. Then it says a height for the lighthouse, which I cant see, but I would figure it out if shown. If a boat is in an ocean or sea, it's always on sea level, which is 0. The fish is 10 meters below sea level, or 0, making it -10. If you add on to -10, where the fish is, until it gets to 30, where Scottie is, you get 40 meters of distance.