algebra
posted by Samantha .
Camille can swim against the current at 1.5 m/s and with the current at 3.5m/s. Write an equation that expresses each fact. How fast can she swim in still water?

the upstream and downstream speeds differ by twice the current speed, or 2 m/s.
so, stillwater speed is 2.5 m/s
up = s+r
down = sr
s = (up+down)/2 = (1.5+3.5)/2 = 2.5