In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

[EX Q]: Problem: a 100 - litre mixture of milk and water contains 36 litres of milk . ' x ' litres of this mixture is removed and replaced with an equal quantum of water . if the process is repeated once , then the concentration of the milk stands reduced at 16 % . what is the value of x ? 
Options: a ) 37.5 litres , b ) 36.67 litres , c ) 37.67 litres , d ) 36.5 litres , e ) 33.33 litres
[EX A]: e

[EX Q]: Problem: find value of x : ( 422 + 404 ) ^ 2 − ( 4 × 422 × 404 ) = x . 
Options: a ) 234 , b ) 267 , c ) 324 , d ) 356 , e ) 577
[EX A]: c

[EX Q]: Problem: if ( a - b - c + d = 12 ) and ( a + b - c - d = 6 ) , what is the value of ( b - d ) ^ 2 ? 
Options: a ) 4 . , b ) 9 . , c ) 12 . , d ) 16 . , e ) 64 .
[EX A]:
b