Assuming 18x18 refers to 18 inches by 18 inches,
each tile has an area of 1.5*1.5 = 2.25 sq ft.
214 sq feet at 2.25 sq feet per tile = 214/2.25 = 95.11... so 96 tiles.
That also assumes that the area to be covered is well behaved and that nearly all the offcuts are reused.
67 tiles.
start with 38 tiles.
192 tiles
118
288
12...
10
The answer will depend on the units used for measuring the tiles which you have failed to specify.
18" x 18" = 1.5' x 1.5' = 2.25 square feet90/2.25 = 40 tiles.
The answer depends on the measurement units used for 18x18.
22.2 tiles so buy 23 tiles.
220