Let
x represent James's speed and
y represent the speed of the current. Since upstream the current goes against him,

describes the speed upstream, and since downstream the current goes with him,

describes the speed downstream.
Use elimination to solve for
x:

or 3.5 miles per hour for James in still water. Substitute
y into either original equation:

or 5.5 miles per hour for the current. As far as an equation, you can use

, where
x is the number of hours James has paddled in still water and
y is the distance he has traveled (in miles).