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'.

[Q]: Problem: a is two years older than b who is twice as old as c . if the total of the ages of a , b and c be 12 , the how old is b ? 
Options: a ) 10 years , b ) 4 years , c ) 6 years , d ) 15 years , e ) 16 years
[A]: b


[Q]: Problem: two trains of equal length are running on parallel lines in the same directions at 46 km / hr . and 36 km / hr . the faster trains pass the slower train in 144 seconds . the length of each train is : 
Options: a ) 82 m , b ) 150 m , c ) 172 m , d ) 200 m , e ) none of these
[A]: d


[Q]: Problem: if 25 % of a class averages 80 % on a test , 50 % of the class averages 65 % on the test , and the remainder of the class averages 90 % on the test , what is the overall class average ? 
Options: a ) 60 % , b ) 65 % , c ) 70 % , d ) 75 % , e ) 80 %
[A]:
d