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: if 25 % of x is 30 less than 20 % of 1000 , then x is ?
Options: a ) 188 , b ) 216 , c ) 156 , d ) 680 , e ) 121
[EX A]: d

[EX Q]: Problem: if n is an integer , f ( n ) = f ( n - 1 ) - n and f ( 4 ) = 14 . what is the value of f ( 6 ) ?
Options: a ) 3 , b ) 0 , c ) 1 , d ) 2 , e ) 4
[EX A]: a

[EX Q]: Problem: the age of somu is one - third his father ' s . 9 years back he was one - fifth of his father ' s age . what is his persent age ?
Options: a ) 11 , b ) 18 , c ) 14 , d ) 12 , e ) 10
[EX A]:
b