Since they stated that there is 20 yards of fencing surrounding the garden,
We are safe to assume that 20 yards is the perimeter.
We can find the length by
20 yards - (3yards x 2) = 14 yards
14 yards / 2 = 7 yards
The length would then be 7 yards derived from the formula of a perimeter:
2Length + 2Width = Perimeter.
To find the area, we simply just multiply the Length by its Width like so:
7 yards x 3 yards = 21 yards^2
Answers:
Length = 7 yards
Area = 21 yards^2