Suppose A pours into B's container for the first time, and the alcohol is X liters, and B pours out Y liters of alcohol solution for the second time.

x/( 15+x)=0.25

The solution is x=5.

y * 0.25+( 1 1-5)/( 1 1-5+y)= 0.625

The answer is y=6.

A: Omit.