speed = distance/time,
You can kind of tell that, because the units of speed is km/h ( or m/s, or miles/hour — depending on the situation).
Now if you apply your algebra skills, you might discover that
time = distance/speed
Plug in the data:
time = 100 km / (80 km/h)
After application of algebra skills again you can see that the units will simplify to simply h.
time = 1.25 h
