Problems involving speed, distance, and time are integral to other problems or could stand on their own. The key relationship to remember is that speed = distance divided by time. Depending on how you like to approach math problems, you can also remember 60D Street, which allows you to infer relationships between speed, distance, and time.
Another key element to this type of problem is being able to deal with time. You must be able to add and subtract time, keeping in mind that there are 60 minutes in an hour (not 100!). Common errors like that can doom problems. The last thing to remember regarding time is that you will need to be able to convert between minutes and fractions of an hour. For example, 30 minutes is 0.5 hours. Likewise 20 minutes is 0.333 hours.
These small math issues have a tendency to cause headaches for mariners - just take it slow and approach each problem with a critical eye....don't rush!