Given:
The distance is 240 km.
The time difference from 9 AM to 12 PM is 3 hours.
To find the speed:
We know that,
[tex]\begin{gathered} \text{Speed}=\frac{\text{Distance}}{\text{Time}} \\ =\frac{240}{3} \\ =80\text{ km/h} \end{gathered}[/tex]Hence, the speed of the bus is, 80km per hour.