Assuming rotation is about origin, then
R180: (x,y)->(-x,-y)
So
A(6,8)->A'(-6,-8)
B(6,12)->B'(-6,-12)
C(10,12)->C'(-10,-12)
Answer: Length of fence along the diagonal is 28.3 feet.
Step-by-step explanation:
Since we have given that
The Blackburn family has a square field ,
Area of square = 40000 ft square
As we know the formula,
Area of square = Side x Side
40000 = slide

20 ft = Side
But Blackburn wants to put a fence diagonally through the field ,
As we know the formula for "Diagonal of side" i.e.
Diagonal of square 
Diagonal of square 20
So,
Length of fence along the diagonal = 20 x 1.41 = 28.3
Hence, length of fence along the diagonal is 28.3 feet.
Hope this helps!
M&0 are similar but not congruent