Write this expression with a positive exponent and then simplify.
9a^-1

When you have a negative exponent, you move the base with the negative exponent to the other side of the fraction to make the exponent positive.

For example:

or

or  

or  

   Make the exponent positive

       (this is as far as you can simplify)

answer: 2 litters juice bottle

half of a gallon is 50% of a full gallon 2 litters of juice is 52% of a full gallon

hope this ^_^