You can solve this by setting up ratios that when cross-multiplied cancel out the units. For example, having a value with a unit of miles in the numerator and seconds in the denominator multiplied by a value with a unit of seconds in the numerator and minutes in the denominator would cancel out the seconds and leave you with a ratio of miles over minutes.
You can convert seconds to minutes (if seconds was on the bottom of a fraction) by multiplying by the number of seconds in a minute over one minute.
Multiply the numerators and denominators separately, cross out canceled units, and simplify if needed. "Crossed out" units are in italics. Units that are kept are in bold.
2+(1/3) miles x 60 seconds x 60 minutes = 8400 miles
1 second 1 minute 1 hour 1 hour
8400 miles per hour
