Put the information from the question into an equation: we know that Olivia added an unknown amount of water to her water bottle to her 6oz. of water to get a total of 32oz. In the equation, we can let w equal the amount of water she added. Then you isolate w to find how much water she added.
6oz. + w = 32oz.
w = 32oz - 6oz
w = 26oz.
Therefore she added 26oz.