Answer:
20 m/s. 
Step-by-step explanation:
From the question given above, the following data were obtained:
Distance travelled = 600 m
Time taken = 30 s
Speed =? 
Speed can be defined as the distance travelled per unit time. Mathematically, it is expressed as:
Speed = Distance /time 
With the above formula, we can easily calculate the speed of the bus as follow:
Distance travelled = 600 m
Time taken = 30 s
Speed =? 
Speed = Distance /time 
Speed = 600 / 30
Speed = 20 m/s
Therefore, the speed of the bus is 20 m/s.