You can put this solution on YOUR website! Poorly worded problem
You probably mean the the car traveled 100 km in 1.25 hours
We would not have enough info to calculate an average if the car traveled 100 km after 1.25 hrs
since we would not have the distance travelled in the 1.25 hours nor the time of the 100 km trip.
r*t=d
r=d/t
r=100/1.25=80 kph