Problem: the ratio between the current age of a and b is 6 : 7 . if b is 4 years old than a . what will be the ratio of the ages of a and b after 4 years ? 
Options: a ) 7 : 8 , b ) 8 : 9 , c ) 4 : 6 , d ) 4 : 8 , e ) 5 : 8
a