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: pure milk costs 3.60 per litre . a milkman adds water to 25 litres of pure milk and sells the mixture at 3 per litre . how many litres of water does he add ? 
Options: a ) 2 litres , b ) 5 litres , c ) 7 litres , d ) 11 litres , e ) none of these
[EX A]: b

[EX Q]: Problem: if 45 - [ 28 - { 37 - ( 15 - * ) } ] = 59 , then * is equal to : 
Options: a ) - 29 , b ) - 19 , c ) 20 , d ) 29 , e ) 39
[EX A]: c

[EX Q]: Problem: a certain number of horses and an equal number of men are going somewhere . half of the owners are on their horses ' back while the remaining ones are walking along leading their horses . if the number of legs walking on the ground is 90 , how many horses are there ? 
Options: a ) 10 , b ) 12 , c ) 14 , d ) 16 , e ) 18
[EX A]:
e