Let x be Debbie 's speed in still water .
Let t be Debbie 's time downstream .
20 minutes 1 /3 hour
velocity distance /time
Debbie 's speed upstream in miles per hour x - 4 5 (t 1 /3 )
Debbie 's speed downstream x 4 5 /t
Debbie 's speed is x 5 (t 1 /3 4
Or x 5 /t - 4 (5 /t ) - 4 (5 (t 1 /3 4
5 /t - 5 (t 1 /3 4 4
5 (t...






