For this case, the first thing you should keep in mind is the speed unit.
The correct units are:
12 Km / hour
Then, we use the following equation:
d = v * t
Where,
d: distance
v: speed
t: time
Clearing t we have:
t = d / v
Substituting values:
t = 240/12
t = 20 hours
Answer:
it takes to travel 240 km about:
t = 20 hours