Question

side=?, perimeter=80, area= ?

Answer 1

Perimeter of sq = 4*side
side = perimeter/4
= 80/4
20

So, area of sq = side*side
= 20*20
=400 sq unit.

Hope it helps...

Answer 2

FOR FINDING THE SIDE OF A SQUARE-

Perimeter of square = 4*side

To find the side we will go with this formula,
Side = Perimeter/4
         = 80/4
Side = 20.

So, area of square = side*side
                                   = 20*20
                                   = 400 sq. unit.