How can I cut a 27×27 square into 8 incomparable rectangles?
A rectangle with width w and height x is incomparable with a rectangle of width y and height z iff $w<y\land x>z$ or $w>y\land x<z$. (Assume $\text{width}\le\text{height}$.)
All rectangles must have integer side lengths.
The book Fractal Music, Hypercards and more... by Martin Gardner says
but eight rectangles can tile a square of side 27
Please don't look in the book; there are no answers there.