Acar drives around racetrack for 30 seconds. what do you need to know to calculate the average velocity of the car

The length of the track, L.  Then average velocity magnitude is L/30s

You would need to know the distance of the racetrack to calculate the average velocity.

Show him another sport or something

The boat's velocity relative to the riverbank can be resolved into two components. the component going north is 2.7 m/s and the component going west is 1.2 m/s.we add these two vectors and then find the magnitude of the resultant to get the speed.the magnitude of the resultant vector from adding can be obtained by the pythagorean theorem.    to two significant figures, the boat's speed relative to the riverbank is 3.0 m/s.