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: the tax on a commodity is diminished by 30 % but its consumption is increased by 15 % . find the decrease percent in the revenue derived from it ?
Options: a ) 20 % , b ) 18 % , c ) 15 % , d ) 12 % , e ) 14 %
[EX A]: a

[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: solve the equation for x : 5 x - 14 + 3 x = 4 + 9 - x
Options: a ) 4 , b ) 5 , c ) 7 , d ) 9 , e ) 3
[EX A]:
e