Question

1) the dragon family lives 165 miles away from the castle, and it takes them 3 hours to fly over there.

Answer 1

1) Speed is measured in distance units divided by time units, such as miles per hour. Here, you're given the number of miles traveled and the number of hours it takes, so you can figure tha average speed to be

... speed (or "rate of change") = distance/time = 165 mi/(3 h) = 55 mi/h

2) "speed at the moment" 1.5 hours into the flight means ...

... d. an instantaneous rate of change at 1.5

3) To keep their average speed on target, the dragons must travel at higher than their average speed for a while.