The equations are

u + v = 15.6,   (the speed with the curren)
u - v =  8.8.   (the speed against the currect)

To solve the problem, first add the equations (1) and (2).
In this way you will find u.
Then find v from any of the two equations.


Explanations:


1.  u is the velocity in still water, in mph.
    v is the current velocity, mph.


2.  When the team rowing with the current, its speed relative to the bank river is u+v.

    When the team rowing agoinst the current, its speed relative to the bank river is u-v.