Question 633335
Let J be John's speed and let S be the stream's speed.

12/(J+S)=2

12/(J-S)=3



12=2J+2S


12=3J-3S




 36=6J+6S

-24=-6J+6S



12=12S

S=1

12=2J+2(1)

J=5

So John's speed is 5mph and the current speed is 1mph.