A car moves 100 metres westward in 4 seconds, and 80 metres eastward in 2 seconds. Find the average speed of the car.

Total distance covered by the car = 100 meters + 80 meters = 180 meters
Total Time taken = 4 seconds + 2 seconds = 6 seconds
Average speed=?

Average speed = $\frac{\mathrm{Total} \mathrm{distance} \mathrm{covered}}{\mathrm{Total} \mathrm{time} \mathrm{taken}}$

Substituting the values in the equation, 
Average speed = $\frac{180}{6}$= 30 m/s

Therefore, the average speed of the car will be 30 m/s.