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.