Answer: 
Step-by-step explanation:
Given: Perimeter of triangular garden = 
The sum of two sides of the garden = 
Perimeter is the sum of all sides of a triangle.
Third side = Perimeter of triangular garden - sum of two sides of the garden

The expression represent the third side =
.
6 3/3 = x + 2/3
18/3 = x + 2/3
18/3 - 2/3 = x
16/3 = x
5 1/3 = x
1:8 because there’s only one green to 8 colours
I am sure it B hope I helped