Answer
See diagram. Call the bricks A, B, and C starting from the bottom.
Brick C's CG is marked with an "x". It must be supported by brick B beneath it.
The CG of the system of bricks B and C is midway between their CGs, and marked with a small circle. This is 1/4 of a brick length away from the right-hand end of brick B.
This CG must be supported by brick A beneath it.
With three bricks, the maximum overhang is achieved when the top brick extends 3/4 of a brick beyond the end of the bottom brick.
