Answer:
6.5 miles per hour
Step-by-step explanation:
At first, Jim was paddling against the current for 3 hours. Then, he paddled for 1 hour with the help of the current.
Let x be Jim's rate without the current and y be the rate of the current:
[tex](x-y)*3=12\\(x+y)*1=17[/tex]
By solving the linear system, we can find the rate of the current y:
[tex]x=17-y\\(17-y-y)*3=12\\y=\frac{39}{6}\\y=6.5\ \frac{miles}{hour}[/tex]
The current has a rate of 6.5 miles per hour.