Just remember the acronym DIRT; Distance Is Rate*Time, or in your case you would do Speed*Time.
Using that, we can develop formula's for Speed and Time.
Since D=r*t, we can divide by t to get R=d/t
We can also do the same to find time, which would be T=d/r
Distance = Rate * Time
Speed (Rate) = Distance / Time
Time = Distance / Speed (Rate)
:)