The difference between 91 and 13 is: 
The difference between 68 and 63 is: 
The difference between 94 and 13 is: 
The difference between 91 and 10 is: 
The difference between 81 and 13 is: 
The difference between 91 and 33 is: 
The difference between 98 and 10 is: 
The difference between 91 and 13 is: 