We need to calculate first the number of ounces left in the bottle:
20 oz - 8 oz = 12 oz.
Now we want to find what percent (x) of 20 oz is the left amount 12 oz.
So we use the expression for percent:
x times 20 = 12
x * 20 = 12
Therefore solving for x we get:
x = 12/20
x = 0.6
which in percent corresponds to 60%
