The equipment storage room where she works is same as the shape of a rectangle, a 4-sided shape with lengths and width. The perimeter of a rectangle is given by the formula
p = 2(L + B)
where L is the length, B is the width and p is the perimeter.
Therefore, if the the room is 3 meters longer than it is wide an the perimeter is 18 meters,
Perimeter = 2 · width + 2· lenght W = L - 3 18 = 2 · ( L - 3) + 2 · L 18 = 2 L - 6 + 2 L 18 + 6 = 4 L 24 = 4 L L = 24 : 4 = 6 m W = 6 - 3 = 3 m The width is 3 m.