The difference between 91 and 11 is: 
The difference between 77 and 66 is: 
The difference between 94 and 11 is: 
The difference between 91 and 10 is: 
The difference between 21 and 11 is: 
The difference between 91 and 51 is: 
The difference between 92 and 13 is: 
The difference between 91 and 11 is: 