Alandscape architect is planning a new nature in the middle of an urban campus. she wants the length to be twice the width and wants to put a 3foot high retaining wall around the perimeter. there will be 300 total feet of wall installed. how wide will this area be

In order to find the width, we will first allot variables to the unknown quantities.
Let the width be x
The length then becomes 2x

The length of the wall installed will be equivalent to the perimeter of the area. Let us assume that the area is rectangular. Thus,
2(length + width) = perimeter
2(2x + x) = 300
3x = 150
x = 50

The width of the area is 50 feet.