The difference between 31 and 13 is: 
The difference between 78 and 69 is: 
The difference between 37 and 13 is: 
The difference between 31 and 10 is: 
The difference between 91 and 13 is: 
The difference between 31 and 13 is: 
The difference between 39 and 11 is: 
The difference between 31 and 13 is: 