Tiles that are two feet on a side cover 4 square feet. 378 of them cover 1512 square feet.
Since a 12x12 tile is one square foot, then 38 12x12 tiles will cover 38 square feet.
Two tiles will suffice since they will cover 36 square feet.
Each tile covers 4 square feet. You will need 24.75 tiles to cover the area.
500/1.78 = 281 tiles
If the 6x12 tiles are in inches, it will take two of them to cover a square foot. You will need 210 of them.
157 18 by 18 tiles are needed to cover 352 square feet.