A 9×7 rectangle is tiled with tiles of the two types: L-shaped tiles composed by three unit squares (can be rotated repeatedly with 90∘) and square tiles composed by four unit squares.
Let n≥0 be the number of the 2×2 tiles which can be used in such a tiling. Find all the values of n. geometryrectanglerotationinequalitiescombinatorics proposedcombinatorics