Let width = X
Then length would = 3x
The perimeter is 2 times the length + 2 times the width, so half the perimeter would be the length plus the width.
L + W = 1/2 perimeter
L +w = 48
Replace L and W withe the variables from above:
3x + x = 48
Simplify:
4x = 48
Divide both sides by 4:
x = 48/4
x = 12
Now you have a value for x, replace x with 12 in the variables:
Width = x = 12 cm
Length = 3x = 3*12 = 36 cm
