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'.

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
b

Problem: a number is doubled and 5 is added . if the resultant is trebled , it becomes 123 . what is that number ? 
Options: a ) 12 , b ) 29 , c ) 27 , d ) 18 , e ) 99
d

Problem: rahul played weel in this season . his current batting averagge is 50 . if he score 78 runs in today match . his batting average will become 54 . how many matches had he played in this season . 
Options: a ) 8 , b ) 10 , c ) 9 , d ) 6 , e ) 5

d