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: a rower whose speed is 2.5 km / hr in still water rows to a certain point upstream and back to the starting point in a river which flows at 0.5 km / hr . what is the rower ' s average speed ( in km / hr ) for the total journey ? 
Options: a ) 2.2 , b ) 2.3 , c ) 2.4 , d ) 2.5 , e ) 2.6
c

Problem: how many numbers from 10 to 1000 are exactly divisible by 9 ? 
Options: a ) 100 , b ) 10 , c ) 11 , d ) 12 , e ) 14
a

Problem: if a ( a + 2 ) = 35 and b ( b + 2 ) = 35 , where a ≠ b , then a + b = 
Options: a ) - 5 , b ) - 6 , c ) - 7 , d ) - 2 , e ) - 10

d