Speed is distance traveled over time.
Example:
You walk 10 miles in 2 hours, so 10 miles / 2 hours = (10 miles / 2 hours) =
5 miles/hour
Always include units, since in some cases you many need to convert things to match the units you need in the final answer, like if I wanted miles/second I would do:
5 miles/hour X 1 hour/60 minutes X 1 minute / 60 seconds.