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: in a class of students , 2 / 3 of the number of girls is equal to 1 / 4 of the total number of students . what is the ratio of boys to girls in the class ? 
Options: a ) 1 / 3 , b ) 2 / 3 , c ) 4 / 3 , d ) 5 / 3 , e ) 7 / 3
[EX A]: d

[EX Q]: Problem: jacob is 39 years old . he is 3 times as old as his brother . how old will jacob be when he is twice as old ? 
Options: a ) 63 , b ) 64 , c ) 65 , d ) 76 , e ) 67
[EX A]: c

[EX Q]: Problem: the mean of 50 observations was 36 . it was found later that an observation 48 was wrongly taken as 21 . the corrected new mean is : 
Options: a ) 36.54 , b ) 36.58 , c ) 36.23 , d ) 36.14 , e ) 36.81
[EX A]:
a