The difference between 31 and 23 is: 
The difference between 51 and 12 is: 
The difference between 34 and 23 is: 
The difference between 31 and 20 is: 
The difference between 81 and 23 is: 
The difference between 31 and 13 is: 
The difference between 38 and 20 is: 
The difference between 31 and 23 is: 