Hmm... The question is a bit confusing. I think you mean:
Use the "sub" and "sup" to get base 2 or something raised to any power.
Margot is sewing a ribbon on a seam along the perimeter of a square pillow. The side length of the pillow is 2 x2 +1 inches, and its perimeter is 4(2x2 + 1) inches. If x = 3.5, how much ribbon does she need?
Pretty obvious. 4(2x2 + 1) inches = 4(2*3.5*3.5 + 1)
= 4(25.5)
= 102 inches
We 4th graders know that 4 times of one side of a square = perimeter.
You may need to improve this question a bit.
Margot is sewing a ribbon on a seam along the perimeter of a square pillow. The side length of the pillow is 2 x2 +1 inches, and its perimeter is 4(2x2 + 1) inches. If x = 3.5, how much ribbon does she need?