You would have 79 tiles.
That would depend on the size of the tiles.
You would need 173 tiles (you would have fractions of tiles left over)
None. No number of gray tiles will make a white tile.
81 tiles squared because if it's a square then it would be 9x9 which is 81
You would need 358 tiles.
Assuming you mean the tiles are 16 inches square - you would need 169 tiles.