Amy needs 6/8 gallon of fruit juice to make punch. she needs an equal amount of sparkling water. how much sparkling water does she need?

I believe it is 6/8 gallon of sparkling water also.
because according to the problem she needs 6/8 gallon of fruit juice to make a punch and an EQUAL amount of sparkling water. Thus, the equal amount of 6/8 gallon of fruit juice is also 6/8 gallon of sparkling water.
The work there is EQUAL AMOUNT = Meaning the same amount.
You did not state any other problem or given any data. You’re just asking about the equal amount of fruit juice.

6/8 gallon of fruit juice
x gallon of sparkling water = ?

If you would like to know how much sparkling water does Amy need to make punch, you can calculate this using the following steps:

an equal amount: x = 6/8

Amy will need 6/8 gallon of sparkling water to make punch.