Bottle A contains more soda than Bottle B. Pour from Bottle A into Bottle B as much soda as B already contains. Now pour from B into A as much soda as A now contains. Then pour from A into B as much soda as B now contains. Each bottle now contains 64 ounces. How many more ounces of soda were in Bottle A than Bottle B at the beginning?
+4 Let 
be the amount of soda contained by Bottle A and 
be the amount of soda contained by Bottle B. We can track the changes in amounts of soda in each bottle. First, Bottle A contains ounces, and Bottle B contains . At the next step, A is reduced by ounces, and B gains ounces, so A has 
and B has 
ounces. Then, A is increased by 
ounces and 
is reduced by the same, so A has 
and B has 
ounces. Finally, B is increased by ounces and A is decreased by the same, so A has 
ounces and B has 
ounces. We are given that 
, and we are looking for . Adding to 
gives 
. Adding 
to gives 
, or 
. So, 
, or 
. Thus, 
ounces.
