The description of the garden fits that of 3 squares arranged side-by-side. The area of each of those would be 100 ft², so their side length would be ...
s = √A= √(100 ft²) = 10 ft
This dimension is the width of the garden, whose length is 3 times this amount.
The length and width of the garden are 30 ft and 10 ft, respectively.
