Since the rectangle dimensions are 6 inches and 11 inches, the side length of the biggest square that can be made is 6 inches:
The area of a square is given by its side length squared, so we have:
[tex]\begin{gathered} s=6 \\ A=s^2 \\ A=6^2 \\ A=36\text{ in}^2 \end{gathered}[/tex]Therefore the area of the biggest square is 36 in².