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: total 85 matches are conducted in knockout match type . how many players will be participated in that tournament ? 
Options: a ) 85 , b ) 81 , c ) 53 , d ) 82 , e ) 84
[EX A]: e

[EX Q]: Problem: the sum of ages of 5 children born at the intervals of 3 years each is 80 years . what is the age of the youngest child ? 
Options: a ) 3 years , b ) 4 years , c ) 6 years , d ) 7 years , e ) 10 years
[EX A]: e

[EX Q]: Problem: john want to buy a $ 100 trouser at the store , but he think it â € ™ s too expensive . finally , it goes on sale for $ 80 . what is the percent decrease ? 
Options: a ) 20 % , b ) 30 % , c ) 40 % , d ) 50 % , e ) 60 %
[EX A]:
a