Final answer:
The third side of the fence is approximately 23.2 meters long. So, the correct answer is A.
Step-by-step explanation:
To find the third side of the fence, we can use the law of cosines. The law of cosines states that for a triangle with sides a, b, and c, and the angle between sides a and b denoted by α, the third side c can be found using the formula:
c = sqrt(a^2 + b^2 - 2ab * cos(α))
Using the given information, we can substitute the known values into the formula:
c = sqrt(30.3^2 + 18.5^2 - 2 * 30.3 * 18.5 * cos(61))
c ≈ 23.2m
So, the correct answer is A.