Task: Question Answering
Input (English): Problem: solution x is 10 % chemical a and 90 % chemical b by volume . solution y is 20 % chemical a and 80 % chemical b by volume . if a mixture of x and y is 12 % chemical a , what percent of the mixture is solution x ? 
Options: a ) 80 % , b ) 75 % , c ) 70 % , d ) 65 % , e ) 60 %
Output (English): a