Task: Question Answering
Input (English): Problem: how many kg of pure salt must be added to 100 kg of 10 % solution of salt and water to increase it to a 25 % solution ? 
Options: a ) a ) 6.7 , b ) b ) 1.3 , c ) c ) 9.6 , d ) d ) 20 , e ) e ) 7.9
Output (English): d