As given by the question
There are given 4.5 ounces of the mix for 6.5 ounces of water.
Now,
If 4.5 ounces of the mix for 6.5, then for the 1 ounces will be:

Then,
For the 108 ounces of mix will be:

Hence, 155.52 ounces of water would need to for 108 ounces of mix.