How many 2.5 inch by 6 inch tiles will fit on a back splash that is 2.5 feet tall and 8 feet long?

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.