Read the Sudoku help page for the rules, and the techniques potentially required to solve BrainBashers Sudoku.

An XY-Wing is a very advanced technique which can eliminate certain candidates from squares. Its name comes from the pattern formed by the digits and is not related to X-Wing.

We are looking for three squares, each of which contains exactly two digits. The first square contains **XY** and we require a buddy of this square to contain **XZ**. We then require another buddy of the **XY** square to contain **YZ**.

Any squares that are buddies to both **XZ** & **YZ** cannot contain **Z**. Why? Because it doesn't matter whether the **XY** is **X** or **Y**, the **Z** will be in either **XZ** or **YZ** and hence can be removed from their buddies.

In this Sudoku **X**=5, **Y**=7 & **Z**=3. R3C9 is **XY**. R6C9 is **XZ**. R3C5 is **YZ**. So no buddies of both R6C9 and R3C5 can contain <3>

In this Sudoku **X**=2, **Y**=5 & **Z**=3. R4C6 is **XY**. R6C5 is **XZ**. R7C6 is **YZ**. So no buddies of both R6C5 and R7C6 can contain <3>.

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