Write a system of equation based on the problem⇒First equation depicts "the width of her garden is one-third the length"


⇒Second equation depicts "the perimeter is 40 feet"
perimeter = 40
2l + 2w = 40
2(l + w) = 40
l + w = 40/2
l + w = 20
Solve the system of equation, substitute
as w to the second equation to find the lengthl + w = 20

Equalize the denominators


Simplify the numerators

4l = 20 × 3
4l = 60
l = 60/4
l = 15
The length is 15 feetSubstitute the value of l to the first equation to find the width

w = 5
The width is 5 feet