Answer:
25km/h
Step-by-step explanation:
This is a trick question, the average speed in this case does not really depend on calculation or extrapolation, it just refers to an event that is yet to occur,
In other words, if you want to achieve an average speed of 25km/h for 23km, then you should drive your car at a constant speed of 25km/h, any variation in speed may cause a change in your average speed at the end.