Respuesta :

Answer:

y = 20 - x

Step-by-step explanation:

Perimeter of a rectangle = 40 units

2 * ( length + width) = 40

  2* (x + y) = 40    {Divide both sides by 2}}

     x + y = 40/2

     x + y = 20       {Subtract x from both sides}

            y = 20 - x