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 river flowing at 2 km / hr , a boat travels 40 km upstream and then returns downstream to the starting point . if its speed in still water be 6 km / hr , find the total journey time . 
Options: a ) 10 hours , b ) 12 hours , c ) 14 hours , d ) 15 hours , e ) none of these
[EX A]: d

[EX Q]: Problem: a car ferry can hold up to 70 tons of cargo . what is the greatest number of vehicles that the ferry can carry if half the vehicles are cars with an average ( arithmetic mean ) weight of 0.75 tons and half of the vehicles are trucks with an average ( arithmetic mean ) weight of 4 tons ? 
Options: a ) 14 , b ) 20 , c ) 28 , d ) 32 , e ) 36
[EX A]: c

[EX Q]: Problem: solve below question 2 x - 1 = 17 
Options: a ) - 8 , b ) - 9 , c ) - 5 , d ) - 4 , e ) 9
[EX A]:
e