Tiles that are two feet on a side cover 4 square feet. 378 of them cover 1512 square feet.
Two tiles will suffice since they will cover 36 square feet.
start with 38 tiles.
Since a 12x12 tile is one square foot, then 38 12x12 tiles will cover 38 square feet.
500/1.78 = 281 tiles
157 18 by 18 tiles are needed to cover 352 square feet.
You will need at least 67 tiles. This will cover 150.75 square feet.
Each tile covers 4 square feet. You will need 24.75 tiles to cover the area.
It will require a minimum of 1,462 tiles. That number will cover about 1,850.34 square feet.