The negative change indicates that two 100 euro bills would not be enough to cover the total cost
Let's go through the calculations step by step:
1. Convert the back splash dimensions from feet to inches:
- Back splash height:

- Back splash length:

2. Calculate the area of the back splash and the area of a tile:
- Back splash area:

- Tile area:

3. Calculate the number of tiles needed:
- Number of tiles:

4. Calculate the total cost before tax:
- Total cost before tax:

5. Calculate the total tax:
- Total tax:

6. Calculate the total cost after tax:
- Total cost after tax:

7. Calculate the change after paying with two 100 euro bills:
- Payment:

- Change:

The negative change indicates that two 100 euro bills would not be enough to cover the total cost. In fact, you would need additional money to cover the full amount of 10176 euros. There appears to be a misunderstanding, either in the cost of the tiles or the payment amount, as two 100 euro bills would only amount to 200 euros, which is far less than the total cost calculated.