Final answer:
The large fountain uses 29 liters more water than the small fountain.
Step-by-step explanation:
The question asks how much more water the large fountain uses compared to the small fountain.
To find this out, you need to subtract the amount of water the small fountain uses from the amount the large fountain uses.
So the calculation is 97 liters (large fountain) - 68 liters (small fountain) = 29 liters.