My friend sets out walking at a speed of 3 miles per hour. i set out behind her 5 minutes later at 4 miles per hour. when i start walking, how many miles has my friend traveled?

The formula for this is d=rt  where d= distance, r= rate of travel, and t= time
d= 3(.083)  (5 minutes divided into 60 minutes per hour)
You could also convert the miles per hour to miles per minute and use the 5.  3/60= .05 miles per minute.
d= .05(5)
d= .25 miles
d= .249 miles