The difference between 64 and 21 is: 
The difference between 81 and 69 is: 
The difference between 67 and 21 is: 
The difference between 64 and 20 is: 
The difference between 34 and 21 is: 
The difference between 64 and 41 is: 
The difference between 72 and 29 is: 
The difference between 64 and 21 is: 