The difference between 61 and 21 is: 
The difference between 68 and 15 is: 
The difference between 69 and 21 is: 
The difference between 61 and 20 is: 
The difference between 51 and 21 is: 
The difference between 61 and 51 is: 
The difference between 67 and 29 is: 
The difference between 61 and 21 is: 