Question 1120630
Draw this 
The width of the fence is x 
There are two widths for 2x
The rest, 28-x is the length of one side
A=x(28-x)=-x^2+28x
From calculus or vertex = -b/2a, the x value is -28/-2=14
x is 14
2x=28
Max area is 392 yds^2.