Hello,
Please, see the attached file.
Thanks.
Circular pen means you are going to use Area = Pi(r^2).
So 78.5 = pi(r^2). Divide by pi on both sides to get r^2 = 78.5/pi. Take the square root of that to get r or radius = approximately 4.99. If you need an exact answer then use

for the next part because you are not done yet.
Plug whatever R you use into the circumference formula of Circumference = 2(pi)(r).
If you use 4.99, you do 2(pi)(4.99) which is approximately 31.35. If you use the exact answer, you do 2(pi)(

) which gives you approximately 31.41.
Either way you'll need about 31 meters of chicken wire but the 31.40796 or ~31.41 is closer to the exact answer.
Answer:
200 KM about 124 miles
Step-by-step explanation:
200 m is only 0.12 miles
200 cm is 78 inches
200 mm is 20 cm or 7.8 inches
We can distribute
2(5)+2(-x)=10-2x
we get
8+10-2x=?
18-2x=?
whatever that ? is, we don't know
multiply both sides by -1
2x-18=-?
add 18 to both sides
2x=18-?
divide bth sides by 2
x=9-(?/2)
whatever the left side it, just divide it by 2 and subtract it from 9