Task: Question Answering
Input (English): Problem: a solution of 90 litres contains milk and water in the ratio 7 : x . if 10 litres of water is added to the solution , the ratio becomes 3 : 2 , find the value of x ? 
Options: a ) 2 , b ) 1.5 , c ) 3.5 , d ) 2.5 , e ) 3
Output (English): c