Final answer:
The large fountain uses 29 liters more water than the small fountain.
Step-by-step explanation:
To find out how much more water the large fountain uses than the small fountain, we can subtract the amount of water used by the small fountain from the amount used by the large fountain.
Large fountain's water usage: 97 liters
Small fountain's water usage: 68 liters
Water usage difference: 97 - 68 = 29 liters
Therefore, the large fountain uses 29 liters more water than the small fountain.