A square tile, a regular hexagon tile, an equilateral triangle tile, and a regular n-sided polygon tile share a common vertex. There are no gaps or overlaps between the tiles. What is n?
I would recommend you start by finding the angle of the n-sided polygon which is 360-90-120-60 = 90 degrees. Since a square is the only regular n-sided polygon with angles of 90 degrees, we know that n = 4.