EXPLANATION
Let's see the facts:
Perimeter = P = 312 m
Length = l = 89m
Width = w = unknown
The perimeter of a rectangle is given by the following relationship:
[tex]P=2(w+l)[/tex]Replacing terms:
[tex]312=2(w+89)_{}[/tex]Applying the distributive property:
[tex]312=2w\text{ + 178}[/tex]Subtracting 178 to both sides:
[tex]312-178=2w[/tex][tex]134=2w[/tex]Dividing 2 to both sides:
[tex]\frac{134}{2}=w[/tex]Simplifying:
[tex]67=w[/tex]Switching sides:
[tex]w=67[/tex]The width of the garden is 67 meters.