help.

[raw belfry]

well we know that all the sides of a square are the same length, right?
so lets call one of the sides of the square "x" it would be 4x = 48

[hasty comet]

if the perimeter of the square is 48cm, then the length of each side must be 48/4 because all the lengths in a square are equal.

so the length of one side of the square = 12cm.

area of square = 12 x 12 = 144cm^2.

so because the areas are equal the area of the rectangle =

8 x y = 144
y= 144/8 = 18 = LM

[raw belfry]

now if we have the length of the sides of the square, we can work out the area of the square.
In the question we have been told that the area of the square and the area of the rectangle are the same.
so we can do this, lets call the side LM on the rectangle "y"
so we have the "area of the square" = 8y (we have 8 from the question)

and you solve

[south rampart]

thanks