Area of each of the tiles = (2.5 * 6) inches^2
= 15 inches^2
Now we have to get down to the case of the backsplash
1 feet = 12 inches
Then
Length of the back splash = 8 feet
= (8 * 12) inches
= 96 inches
Height of the back splash = 2.5 feet
= (2.5 * 12) inches
= 30 inches
Then
Area of the back splash = ( 30 * 96) inches^2
= 2880 inches^2
So
The number of tiles required to fit in the back splash = 2880/15
= 192
So 192 tiles will be required to fit in the back splash. I hope the procedure is clear enough for you to understand.