Help please I suck at geometry.

 21. Perimeter = 48    22 . Perimeter= 36    23.  Perimeter= 72

Step-by-step explanation:

First  you need to find the side length using the area of each of the squares. We know that to find the area of a square you will  have to square one of the side lengths, that means that to find the side length, we will need to find the square root of the area.

21 .  Find the square root of  144.  

       = 12

  The side length is 12 so multiply  it by 4 to find the perimeter because the perimeter is the distance around the shape.  All the side length's of a square are the same and there four sides so multiply it by 4 to find the  perimeter.

   Perimeter = 12 * 4

   Perimeter  = 48  

22.  The same thing with this one, find the square root  and multiply the side length by 4.

     =  9  

 Perimeter = 9 *4  

  Perimeter = 36

23.      = 18  

   Perimeter =  18 * 4  

    Perimeter =  72