When Elvis swims with the current he swims 18km in 2 hours A

When Elvis swims with the current, he swims 18km in 2 hours. Against the current, he can swim only 14km in the same time. How fast can Elvis swim in still water and what is the rate of the current?

D=RT
R=D/T
R=18/2=9 KMH WITH THE CURRENT.
R=14/2=7 KMH AGAINST THE CURRENT.
(9-7)/2=2/2=1 KMH IS THE SPEED OF THE CURRENT.
PROOF:
9-1=8 SWIMMER\'S SPEED.
7+1=8 DITTO