40 is the correct answer. Hope this helps :)
10x^2y^-2 = 10 x (-1)^2 x (-2)^-2 = 10 x 1 x 1/4 = 10/4 = 2 1/2
Answer:
Two boxes will cost
The cost of one tile is approximately 
Step-by-step explanation:
Note that 1 ft = 12 in, then

The area of the floor is

Now

then
144 sq. in - 1 tile,
9540 sq. in - x tiles.
Mathematically,

tiles is needed to cover the floor (67 full tiles).
Each box of tiles contains 45 tiles, so Cristina has to buy 2 boxes. These two boxes will cost
The cost of one tile is approximately 