For this question, one would sum the algebraic lengths of the rectangle, creating a result of 4x + 16.
This is the algebraic perimeter of the rectangle which must be equated to the numerical value of the perimeter, which is 80cm.
Next, one must solve for x, through subtracting 16 from both sides of the equations, then divide both sides of the equation by 4, as follows:
4x + 16 = 80
4x = 64
x = 16