To get the perimeter of a square you take it’s side length times 4. To get the perimeter of a rectangle you take 2 times it’s length and 2 times it’s width and add the product together. So the formula is for square is 4L = P
The formula for rectangle is 2L + 2W = P
If you know the perimeter of a square and rectangle are the same you can set the equations equal to each other.
So 2L + 2W = 4L and since you know the side measurements. You sub them in.
2(4x + 8) + 2(10) = 4(8x) and then solve for x
X = 3/2