# Squares within squares

Consider a $$3\times3$$ grid of $$1\times1$$ squares. Now consider two other grid-squares, the same size as the previous ones, being placed randomly on the $$3\times3$$ grid. The squares must be entirely on the grid, are allowed to overlap over the interior grid lines, and must have each side of the square parallel to a grid line. If the chance that the squares do not overlap is $$\frac{a}{b}$$ for coprime positive integers $$a$$ and $$b$$, find $$a + b$$.

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