Given that,
The given expression is : 
To find,
The value of the above expression when x = 2 and y = 4
Solution,
We have,

Put x = 2 and y = 4 in the above expression.

So, the value of the above expression is 18.
Answer:
62.8 feet
Step-by-step explanation:
Radius of the fencing is:
6+4 = 10 feet
Circumference = 2×pi×r
= 2×pi×10
= 20pi
= 62.83185307 feet