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: the average age of a group of 10 persons was decreased by 3 years when one person , whose age was 42 years , was replaced by a new person . find the age of the new person ? 
Options: a ) 22 , b ) 18 , c ) 12 , d ) 88 , e ) 66
[A]: c


[Q]: Problem: the average of 13 numbers is 60 . average of the first 7 of them is 57 and that of the last 7 is 61 . find the 8 th number ? 
Options: a ) 43 , b ) 30 , c ) 35 , d ) 45 , e ) 50
[A]: a


[Q]: Problem: 8.5 × 6.4 + 4.5 × 11.6 = ? ÷ 4 
Options: a ) 426.2 , b ) 426.4 , c ) 106.6 , d ) 422.4 , e ) 522.5
[A]:
b