For this case, the first thing we must do is find the perimeter of the rectangle. 
For this, we use the equation:
 

Where, 
- w: width of the rectangle 
- l: length of the rectangle 
Substituting values we have: 

We add hour the amount of foot gate on one end: 

Then, the remaining amount of fencing is:
 

Answer: 
Jim has a remaining amount of 17 feet of fencing